Thanks for asking her at JustAnswer
Was the water running when it stopped or you went to turn it on and there was no water?
How cold is it where you are located?
Well I believe one line has an ice block, (I won't say that word) how is that.
If you have a pressure balance faucet valve, only pressure on one side will cause the other to just trickle. The heat just may not be exactly where it needs to be. With those temps you can be just a few inches to far away and it won't work.
Hope this helps, please reply with any other questions about this.
That depends on what type plumbing you have. CPVC pipe will take no freezing, Copper will take a little in short straight runs, pex or wirsbo is very resistant to bursting. The block can be after where the shower line comes off the main trunk line.
Not through the 90's in plumbing. Electrical 90's are sweeps and designed for the tape. Is your shower faucet on an outside wall by chance?
It is possible that the water isn't frozen (opps) at all. You could have a bad cartridge in the shower valve. Do you know what brand the faucet is?
Yes the Moen faucet is very easy to repair. You will need a screwdriver small needle nose pliers, Moen stem puller. This is the stem below.
Get the new stem first, the needle nose is for the "U" clip you have to remove. You may not see anything obvious that is wrong with it.