Sums my thoughts up pretty succinctly too, though as I find the knowledge of nearly all the Genius aside from a few Lead type exceptions being pretty utterly clueless about anything that isn't really easy like water ingress on an iOS device - so you obviously didn't get one of the clever ones. Though the battery falling out probably helped a lot for the drama convincing them lol!
A lucky escape, change the way you pack your MBP so it doesn't get compressed and steer clear of Colgate and other fairy tales you find others doing on youtube