USDT cannot vanish from your wallet. It has to be sent somewhere. Maybe u can post the wallet address that received the USDT.
Exactly that. Vanishing is nonsense. Everybody knows that basically every transaction is visible. OP did you even check what happened? Did your friend create his wallet himself or did anybody else have access to it, or at least the seed?
Sounds all a bit odd.
Problem is, once the money is gone there is nothing that can be done in 99.9% of the cases.