@Brandon9000,
I'd like to think (and I could be really wrong here) that hospital stay would trigger an investigation into why premiums were not being paid. After all, the hospital is billing the carrier ...?
I'm sure this has happened many times. It is a highly plausible scenario. But consider that accident victims are brought in all the time, unconscious people (let's leave amnesia out of the equation), that sort of thing. Those people are admitted, under the emergency, and then the payment issues are figured out later.
I suspect someone who does not regain consciousness or mental capacity would have a guardian appointed for them.