I have had the same thing happen. Went Kayaking with the key in my pocket and dumped several times and the key still worked. Not sure I would COUNT on them being water proof but I sure was lucky/thankful!
I know the feeling. I was at the beach this past summer. Was asked to get something from the 5. Totally forgot to take the key out off my pocket. The key spent a solid half hour submerged in salt water. I took the key apart immediately. It was completely dry inside. I am still using that same key today.