I'm sure this has been addressed somewhere, but I've searched and searched and couldn't find it.

When I try to respond to an offer to trade a buff (Exotic fruit baskets, specifically) with me having the buff, the transactions always fail.
What's up with this? If it's not something available why is it in the trade tool, and if it's something that I don't have the rank to, again, why is it in the trade tool?