Why is there an elf hanging out in my fortress?

I had an elf caravan visit, do some trade and leave. They're definitely gone, because other caravans have come and used the depot. The elves seem to have forgotten one of their folks. He just wanders around my farms and stockpiles.

Is this a bug? What the heck is he doing? Might this have anything to do with our agreement to not cut more than 100 trees per year?

Solution 1:

Could it be your liaison? A liaison comes with each caravan looking for a chance to meet with your leader. Until they get their meeting they will just follow him around.

While your leader is busy, the liaison will stay in your fortress, until you get the announcement "Diplomat Stymied: A diplomat has left unhappy", or until you have the meeting.