Actually I've found that your stuff stays wherever you leave it, even in the wastes. So do bodies for that matter.
If you stash items in the wastelands they can get looted by other folk. I killed the shady "want to blow up Megaton" character in the bar near the beginning of the game, just before he killed the sheriff. Both bodies are still in the bar, right by the door, it's sort of a painful reminder because I think I should have killed shady man faster.
The other day I wandered into the middle of a deserted car park, heard a "WOOOOOSH!" and turned just in time to see a mini-nuke whiz by, slam into a nearby car and set off a chain reaction that killed EVERYONE in the car park, including me. The explosion sent me flying into the air and my body landed on top of one of the nearby buildings.