I've heard of this happening but how rare (or frequent) is this?

I know, you can't fix stupid.

I had 2 guys tell me they got ripped off while trying to buy weed before mid1990's

Pretty common.  

There are two usual scenarios.  

Someone reporting they were robbed of money and when the investigation concludes, it turns out the "robbers" were just collecting on a drug debt owed to the dealer by the "victim".  Drug dealers "front" drugs all the time and then surprise surprise....drug addicts can't pay.  It's still a robbery but those robbers are more likely to get a plea deal than if they had robbed some truly innocent person.  And, that assumes the "victim" actually shows up for court.  Most of the time they don't so the case is dismissed.  

It's also pretty common for drug dealers to set up deals for the purpose of robbing the person coming to buy the drugs.  The "victim" usually starts out by claiming they have no idea who robbed them but their story often falls apart under routine questioning....if the officer taking the initial report is competent in interviewing skills.  

The purpose of the report for the "victim" isn't usually to get a case prosecuted...it's a way of pressuring the drug dealer for more drugs.  

The drug world is a fucked up world full of fucked up people.

We have a bunch of different types.  They don’t happen everyday, but it happens more than people think.  We generally don’t investigate them if we know what they are, and when they complain, we threaten to charge them with filing a false report.  

Rip:  
Someone goes to buy drugs and gets robbed instead of getting drugs.  99% of the time this happens to white suburban kids who go to the hood to buy drugs, or in the downtown districts during bar hours.  This happens usually with just a strong arm or armed robbery, but once in a while they will take the kid to an ATM and make them withdraw max funds from their account, and then tell them their PIN.  


Drug Debt Collection:
Someone owes money and they get beaten because they didn’t pay their debt. Everything they have of value gets taken.  This happens in the area of high drug dealing activity usually.  Sometimes it’s reported to be somewhere else, but 9/10 times they’re reporting it so their spouse or family doesn’t find out why they got robbed.  When they report they were robbed at the location that they claim and it doesn’t make sense, that’s when we usually start to figure it out.


Drug Debt Hostage:
Someone owes drug money and they continually haven’t paid, so they go to the trap house to buy more and instead of being given drugs on a tab, they get held hostage at the house and have to have someone basically “bail” them out by paying their debt.  If it goes too long and they haven’t gotten their debt covered, they usually get beaten pretty good and thrown out into the street.  They then claim they were held hostage but don’t tell us why, though it’s obvious.


Crack Rentals:
You want to buy drugs but don’t have money, so you agree to loan your vehicle (usually nicer vehicles) to someone for a couple hours in exchange for drugs or paying off drug debt.  The vehicle either doesn’t get returned, or the “rental” is a day or more on agreement.  The owner then reports it either stolen or carjacked.  When we hear about what location it was “last seen” or who is reporting it, it usually gets put together real quick.  We will still enter it as stolen, because fuck the people who are dealing.  If the owner presses charges, we get to slap someone with a felony charge.  If the owner refuses to cooperate, we charge the owner with filing a false report.


Fake Drug Ripoffs:
This again is common with stupid white people in the wrong neighborhood or in a downtown district during bar hours.  They go to buy drugs and get fake drugs, be it aspirin instead of coke, or oregano or K2 instead of MJ, or fake syrup shit instead of heroin, and when they realize they got ripped off, they report that they were robbed.  Occasionally they’re dumb enough to report that they were trying to buy real drugs and got ripped off.  Those are the best, because we have an ordinance of Loitering with Intent where we can jail people for even trying to buy drugs or solicit prostitutes.  


When we get these calls, it’s usually pretty obvious what happens and we call them out on it.  I love getting these calls when I’m FTOing a recruit, because it’s a good gauge of the recruit’s common sense and street smarts if they manage to figure it out without me saying so.  I’ve had two recruits in particular immediately pick up the bullshit, one of which also picked up a prostitute who was trying to claim rape from a customer that stiffed her (no pun intended) on the bill.

UnaStamus pretty much nailed it.  Happens all the time, you just have to read between the bullshit, I mean lines.  Same thing with prostitutes claiming rape because the john didn't pay afterwards.

Prob depends on the area. Where I work, a couple times a month, on average.

J-

In my experience it happens often.  Same with “my car was stolen”.  That translates into “I traded my car to a dealer for a crack rock, and now I regret my decision”. I used to see that shit all the damn time

We call that a “J” trade.  Trade car for dope.  Then wanna report it as stolen.  Fuck them.

“Someone robbed me and took the rent money” many times turns out to be a robbery during s drug buy.

The thing I was surprised to learn, was how many  kidnappings, are really  hostage taking, for drug debts owed.   When the dealers don't have the money, and care about the person taken (usually a child) they will come to the police and they the whole story, in hopes of getting them back alive.  

The very first kidnapping I worked, was a teenager, whose father owed a cartel $160,000 in Dallas, Texas.   We got the kid back, but we were lucky, because it was more luck than what we did right on that one.