Tim: Do you think it could have been coming from the bath/shower fittings that are behind that wall? Of course, since this hard rain was the first time you've had the problem, I would guess that the rain was getting in somehow. Just wanted to toss out that idea as another possibility.
We were also in a non-stop hard rain for most of the day on Saturday in NC, but no leaks. However, I'm concerned that sooner or later we'll end up with the same issues.
I'll watch to see what others think, and I know you'll let us know when you get to the bottom of it. Sorry it happened.
2013 Surveyor SP220
2010 Silverado LT 5.3 V8
The world is a great book, of which those who never stir from home
read only a page. - St. Augustine