Long story short, doing a couple transfers from a neighboring state gun shop to NH residents.  People were supposed to contact me to pick up, never have ( it's been 2 yrs one one of them.).

I've informed the gun store of this and to contact their customers, still nothing.

I'm sure the laws are state specific but looking for any guidance from people this has happened to.  Thanks!

2yrs!?  Do you even have a name, address, or phone number?  Check local laws, but you should be able to sell them.

You need to include, if you haven't already, a notice to transfer customers that transfers not picked up within some reasonable period of time, say, 3 months will incur a monthly storage fee, just like a tow truck lot.  If the storage fees plus transfer fees owed exceed the value of the item, it is essentially forfeit to you and you'd be able to take ownership of the item and sell it.

Without such language in your terms, you need to review your state's laws on abandoned property to see what your rights and recourses may be.

I do have that language in the transfer terms posted on my website.  I managed to find one of the owner's info and have called and sent a certified letter, I'll see how that ends up.  The other guy, who knows.  I called my state government and no one seemed to know.  There are clear laws for intangible property (monies/securities etc.) and for storage units but nothing specific for firearms.

I have.
Guy bought two AR complete lowers in January 2013 (paid $150 for one, $480 for the other).
I sent him an email they day they arrived, he emailed back saying he'd be here at 6pm. Didn't show.
After two weeks I sent a reminder, and again he said he would be over that night. Didn't show.

Another two weeks and I emailed him again that a $5 per day late fee would begin the next day. He called and apologized, said he'd been "busy".

Never heard from him again. He ignored the next email, a phone call and a letter.

He lives less than a mile away, so convenience doesn't come into play. My guess is he may have figured out he's a prohibited person.
Both lowers were sold when storage fees exceeded the price on his invoice.

Check for things like mechanics and jewelers, or abandoned property in general.  There probably won't be anything specific for guns, but those other areas may cover it.

Guy bought a silencer and never picked it up. Form approved. That was 5 years ago. I checked every db I could find, even soldiers killed in IRQ/AFG. Nothing.

Still sits in back of safe.

Thanks guys for the info.  These aren't million dollar guns but I have trouble understanding why someone would buy one, then never pick it up.  Maybe they became prohibited after the purchase, who knows?

My primary dealer has a Rhodesian FN FAL that a customer sent to him to have work done to it. My dealer completed the work and the customer never came by pick it up and pay for the services done. It's been at his shop for 7 years now

Update:
Well a certified mail letter prompted one person to come and pick it up, who knows about the other.  
Thanks for the info. everyone!

I've had a couple that sat in the safe while the buyer claimed to be getting their permit
They didn't exactly initiate contact the whole time I was holding their stuff
I had to send them emails
One finally got his permit and claimed his purchase
The other claimed that they'd lost their job and I should sell the gun and forward the money to them, so I did

Umm, that's my rifle. I lost that guys number. Could you provide it for me so he can send it to me

Guy I used to shoot with years ago bought a pistol and dropped it off at some big shot gun smith who was known for certain specialized competition work. The smith had a big back log at the time and had said it would take a while to complete

Due to changing jobs and other things that kept him out of the country and out of the area the guy never got around to picking up his gun.

20 years went by and the guy was in the area taking care of some family stuff and brought along the claim check.

He dropped in with no notice to see the gun smith and handed over the claim check. The smith scratched his head and went searching around the workshop finally coming back with a dusty old box. He opened the box , looked at the gun and read over the work order that was in the box .

" Could you come back in two weeks?"