Man...I really do feel your loss :'(
Not to be "that one guy that's gotta' be a dick", but...what, exactly were the circumstances here?
The mention of the U-Haul has me *assuming* that you were moving to a new place.
I'm curious why your gaming collection would not be one of the 1st things to make sure you unloaded?!
I mean...compared to furniture/beds/other big & bulky things that need multiple people to move-in/unpack - your ~300 games, or so (I would think, at least)...just by virtue of being higher-value and lighter-weight (simple enough to carry in a few boxes w/o help); I'm wondering *WHY* (of all things) would they be left out on a truck overnight?
Also, did you make sure that all of the doors (including the back door) were all securely shut & locked?
Were the keys left in the truck?
I ask, because your average, 'run-of-the-mill' "smash 'n' grabber"/junkie would not be able to easily break-into (much less, hotwire) a vehicle like that.
I'm also considering that it's (sadly) possible that it was an inside-job...think about people who might have had the knowledge of what exactly was in the back of that truck & when (be it friends, family, and/or U-Haul employees).
Again, because a *presumably* empty U-Haul truck is about as far down the list as you can go when it comes to desired vehicles to steal.
Sorry if I come across as a jerk...I'm not one and/or trying to be one; just trying to give you some new/different ideas & perspectives to think about everything from.
All of that said, I'm sure that I could help contribute a few things to help you get re-started w/ your collecting...and I would be happy to do so!