How do I know if my temporary veneer is leaking?

I have four temporary veneers across my top front teeth. Two of the veneers have already fallen off, but been re-cemented by my dentist. He is currently out of town, but I am afraid that one of the veneers is loose again or leaking. I have some sensitivity on that tooth/gum line right now. I have not had a root canal on that tooth. Is this is something I can try to fix myself until he returns Monday? Any suggestions?