You will need to log something to get them into your hands before you can log dropping them into another cache. The method that Bear and Ragged suggested is ideal, but not the only possibility. I think mpilchfamily is leading you astray as there is no "Found" log for a trackable. You will either "Grab" them from your cousins, "Grab" them from "Somewhere Else" or you could "Retrieve" them from the cache that they're in (but since you didn't really do that, that's not the best option in this case.)
Are they both showing as currently being a cache--though not the same one?