Perhaps we should all learn a lesson from this unfortunate incident, no comfort to OP but we should use appropriate rain covers etc or good insurance when we take a camera out in those conditions.
If you read the OP you'll see he had one of the more respected rain covers in use.
I think there's an end of the spectrum that is abuse, and an end that is too careful to really do photography, and where people decide their risk tolerance is becomes a judgement call. And along with it a whole spectrum of gear quality -- I'll shoot my 400/2.8 in the rain without a thought, but the 80-400G with those bellows working in and out goes in the case when it starts raining. It's hard to know what things really were like if you weren't there.
Personally I also think gear damage (or lack of it) has at least as much to do with what you do after the rainstorm, than during.