Just happened to me. My game crashed and when I logged back in I noticed I had 3 grand gems in my inventory from my characters equipment. The equipment they had been in had been replaced by random 750 legendary gear. I Lost:
Ancestral pants with 3 greater affixes
Ancestral amulet with 1 greater affix but a really good roll set
Those were the best pieces in my character inventory. This really sucks. Did I get hacked?