Items missing, possible roll-back?

I recently self-muled a few items. I quite clearly recall picking the items up and putting them into my character's stash, because I had to juggle a few things around to make space. When I logged back onto that character a few hours later, I was surprised to find the items were missing from my stash.

Is this a "roll-back?". What can I do (if anything) to prevent this happening in the future?|||Sounds like what happened to me before. A friend helped me mule a Lem rune and a 3sock ap from my mule to my main char, but when i was about to leave the game with my main char (with the items), the game lagged. After several seconds the game kicked me out. I then joined a new game, and noticed the muled items were gone. Roll-back I thought, and I went on my mule to check if the items had returned there. No sir, they had not. Great.