Pretend you are a plumber from the future. You see a frozen pipe before it bursts. The signs are there: a funny smell from the drain, or no water coming out of a faucet. If you turn a handle and get nada, you have a problem.
Don’t panic. Do not use a blowtorch. Seriously. People do this. They set their walls on fire. Use a hairdryer. Start near the faucet and work your way back. The thawing water needs to escape.
If you can’t reach the icy spot, or the pipe looks cracked, call a pro. Your ego is not worth a flood. Hire the hero with a wrench.