They had already stuck a few items into the items slots to trade back with me, and all the sudden they couldn't put anymore in, for no reason whatsoever.
We confirmed trade so I could get whatever was already in there, then they relogged to continue trading.
3 things were lost and I don't have them-- Neither do they.
The name of that character is Varick, and I was trading on Nur.
Luckily I only lost 3 Urnins.
Also, a mod told me to submit a ticket and I can't find out where to do that, so...