You’ve been lucky then - see @CDR_Shepard above for a PS3 instance. I can say that I managed to completely avoid this in BL2, although I saw it happen twice to my son when he dropped in locally to an on-line game I was already in.
Sadly, my experience on TPS has been abysmal in this one regard though - happened again to my friend last night when he (playing Nisha) joined my (Claptrap) game.
There also seems to be some issue going on with the hotfixes, as I’m getting inconsistent grinder behaviour with purples, and the 150 moonstone backpack SDUs are on offer at Crazy Earl’s when they’re supposed to be blocked until a fix is out to stop the slots disappearing from your inventory. Yet I’m clearly signed in to XBL so I should have the hotfix in place. It is all very odd.