A seal would work. short sweet and likely something expensive for them to replace. Where its guaranteed they’ll be ridiculed at best for being careless.
Under normal situation, no a trader would not let go of the seal, hence him being drunk.
I doubt the guild would be so willing to cause issues with a tavern when their member was assaulting or trying to assault one of the girls, bad PR.
humm.
guild seal could be an amulet of sorts, looks like weight scales, one with a box and the other with a coin, hanging around the neck of a troll head mount saying the guy was a troll