I've had lots of strange things like this happen. I would assume the hot water faucet was dripping, but still shouldn't have been enough to keep it that warm.

There has to be a rational explanation.

Or maybe not. I do believe angels - i.e. God looking out for us - do lots of things. I don't believe God would keep the water warm for any reason however, as it did not greatly benefit the OP for any reason. Unless it is some kind of message or saying "believe!"

I have had many experiences with guardian angels helping me out of tough spots, and it's nothing to make fun of. Again though, the warm water didn't seem like a "tough spot."