Don't items only drop from certain maps? You aren't going to get Blue Fox Hide from a Leather map, only from a Goatskin map (and maybe Toadskin?). The Tonberry minion comes from Boarskin. Other rare crafting mats come from the Peisteskin maps, which are really fun to do in FC parties.

Are you sure your inventory has room for the materials? I don't think you get anything if your inventory is full.