The Facebook group which your item was claimed from will be and written in bold on your Sales page under the item picture

If the group or Party is not present, this can be caused by the customer liking your item, then claiming the item from their Your Liked Items list.  This claims the item from the Claim Page directly, and is not connected to a specific group or Party. If your Party is connected to your Sonlet Social thread, you can find the claim there, and the Party name should be listed.