I can see dropping it water, sand, dirt and mud, but not all three and then have to shoot it without at least wiping it down or rinsing it off (if your around water), and he didn't just 'drop' it in there, he pressed it in there.
If your in a firefight and have to rely on a pistol and dropped it in dirt, then stepped on it so it was really in the dirt, I'm pretty sure you are probably not going to have a chance to pick it up, it'll probably be left there for your 'adversary' to pick it up, wipe it off and use it once you've fled, been killed or captured.
That being said, there is a reason the military chose that side arm years ago and have used it all this time. I don't have the M9, but I do have the 92fs I purchased new and never had a problem with it. I don't think most people would treat their firearms like that anyway. Most will take care of it and use it like it was intended, not throw it in muck and say it's a failure.
I take mine out, shoot it a crap ton, bring it home, clean it, reload some more ammo and get ready to take it out the next weekend. I've got about 2500 rounds through mine since I've had it and it has never had a failure, I've also never dropped it and if I did, I would defiantly make sure it was not damaged before I used it again.
Not trying to piss anyone off, and maybe I'm wrong. I've been wrong before. but that's my 2 cents.