About 2 weeks ago I thought this happened to me but I wasn't quite sure. I was sorting a cargo hold tab completely full of legacy companion gear. I can't remember which sort category I used but after the sort there were a couple slots empty. I wasn't sure if items actually disappeared or if I was mistaken. I have lots of that gear so a couple of lost pieces wasn't a big deal, so I didn't pursue the issue with customer service.
This is something the devs and players should pay more attention to.