Will it be apparent if I have frozen pipes?

I sometimes forget that some of my RV brethren have plastic faucets and shower valves, I have all metal ones. Yes, you could have a cracked shower valve that has only cracked along a mating surface and that will probably drip rather than flow a lot. The chances of that are very small, however. I would assume, given any unknown previous circumstances, the valve cracked due to other circumstance, like over tightening. Freezing usually gets the pipe or fitting that is most exposed to the weather. Depending on temps, there may be multiples.

If ruthless is losing sleep, the way to get good rest is to pressure test the system. If you use air and have a leak, there will be less mess.