Did they test for parvo? For some reason that was my first thought. I've had two dogs succumb to parvovirus and both of them drooled insane amounts at some point. Is he still eating, drinking, behaving normally? Parvo starts with a loss of appetite so I doubt this was it if he's eating fine.
He very well could've gotten into something he shouldn't have. Whatever it is, hope it gets better!
He very well could've gotten into something he shouldn't have. Whatever it is, hope it gets better!