I was just holding a barrel of water while checking a cave for metals, and Ender's Client crashed. It only took about ten seconds to get back in-game, but once I did the barrel was nowhere to be found. Just a minute earlier the same thing had happened, but I wasn't standing next to any objects when it happened. I logged back in and the barrel was right next to me, waiting to be lifted.
The same thing happened a few days ago with a boat, as a matter of fact.
If this is something that's already been mentioned before, I'm sorry for the repeat post but I searched "cave walls" and "lifted items" and got nothing relevant.