Main Rule is: "Trust NO One" (in fact, you shouldn’t trust me when saying this to you :D)
PM me here if you in game, I can give you some items for to amend your loss (Str Gaunts and also some legendary Aura)
Aalso (if you want), you can file a case against him via support ticket but it will require in game proof that you lend the items to him (FB screens are not enough)