Ah, that is true, actually. Furthermore, I'd say it isn't a terrible idea to keep one for yourself even if that is the case, honestly. If it's your Pokemon, then you'd have firsthand knowledge of all their abilities, wouldn't you?

Plus it would be more aesthetically pleasing than the... fairly generic-looking set of keys they seem to have accumulated already. A set of skeleton keys would look a little more elegant, if you ask me.