Nope, still at the parking lot outside of Nashville, there was a com unit on the ground that I ignored, wanted to loot everything first but then coming back to it it was 'dead'.. so I thought.. darn.. need to reload.. which turned out being a bit disappointing..
But I think I am getting slightly better loot so far so I'm redoing it all again, although I have noticed some things are static loot and other are randomized. But in any case, still there so can test it out and let you (and anyone else that might be interested in knowing) know if loot stay where you leave it in a locker.
Edit: Seems to work. Put a crowbar in a locker, saved and logged out completely from the game for a couple minutes, once back the crowbar were still there. So hopefully you can save stuff everywhere but the benefits with the personal Boxes are that they are linked together ?