Oh my... that's a tough situation you are in. Too bad you potty trained her! If she wasn't potty trained I'm sure she wouldn't be gone with your son for too long
and would be back where she belongs.
Is there someone who can drop hints to your son about how much you love her and will miss her?
Dogs do have feelings and I've heard stories where they get really naughty when they are away from home. Devious little buggers!