I think this spot in the game is a perfect place to add a little dialogue. If there is an automatic flag to make Griff's gang hostile if the elf is freed without the gang getting the thief's name, then I would suggest it be switched to trigger a conversation instead. It makes sense that they would be suspicious of the new guys in camp if the elf were mysteriously missing, so perhaps a difficult persuasion check should be required to talk them down.
