Fishfire that exact thing happened to us last year, a rock sheared it clear off. I had to stuff some balled up duct tape into the whole and then wrapped duct tape all around so it would hold water all weekend. When I bought a new drain after the weekend I bought an extra to keep in the trailer just in case it happens again. I thought it was a total fluke that a rock would do that, but apparently not.
2012 Toyota 4-Runner SR5
2012 Jayco Jay Feather Ultra Lite 228