You have my sympathy I was leaving on vacation last week and sprung a leak on the bathroom sink hot water. Did a quickie repair job working left handed under the cabinet access panel.
I still had some pressure loss and the repair failed the next day. So, I shut the water heater input, output and bypass valves off. The cold water line will hold the pressure all night.
We heated water in the coffee pot like in the old days.
Now that we are home I get to remove the bathroom vanity to start my hot water line leak hunt, starting with the hot water buried behind the bathroom drawers.