It is extreemly cold and all water in house was working. Next day all water still working except hot water to the master bathroom sink and shower. There is cold water to the whole house and also hot water except to that master bath sink and shower. Put a heat gun to the hot water pipe for the master bath sink and would get a weak stream of water from the hot side that eventually trickeled out.

Could be a frozen pipe if the piping comes up an outside wall or through an uninsulated space. Keep working with a heat gun.

I agree and if it stays really cold consider allowing a tiny trickle of hot water to drip all night. Moving hot water is hard to freeze