Good thing that the baby is OK. *whew*
This has to be one of the most unusual threads that I've ever seen here on CPF so far!
If you have a photo of what's left of the switch on the light, please post a photo as I'm curious about what sort of damage a little one can do to a tailcap.
Edit
Nevermind. I just re-read your post and realized that the baby actually swallowed the entire tailcap. I thought that he just chewed on it. Please ignore my picture request as I really don't need to see a poopy diaper.