Well, I woke up this lovely 15 degree morning to find no water at all running in the master bathroom. The master bathroom holds the hot water heater.

Upon investigating the rest of the house, I found that the cold water works in the kitchen and second bathroom, along with the outside hose faucet. However, both the other sinks have nothing at all happen when I turn on the hot water.

The only time I've seen something like this before was when the water was shut off to the house as a whole, but since I have cold water in all rooms but one, it can't be that.

I found that something had pushed open the access to the crawlspace under the house when I went investigating this morning. I hopped down there with a flashlight and couldn't see any obvious frozen or burst pipes, but I couldn't see the master bathroom pipes.

I'm assuming I likely have a frozen pipe running to the master bathroom, it's preventing the hot water heater from getting water, and thus preventing the rest of the house from getting hot water?

That's pure guesswork - does anyone have any suggestions on what I can do to diagnose this further?

Well, once I sealed the crawlspace back up, I was able to get water running in the master bathroom within about an hour. It must have been a frozen pipe running to that bathroom.

Still working on getting the hot water restored to the rest of the house.