Originally Posted by OnTheGo
You need to generate some heat from whatever source(s) you have available. After it's thawed, check thoroughly for leaks. And if you continue to use it in freezing temperatures, keep it heated or drain it.
X2 and if possible temporarily move it into a warmed barn or storage facility which will aid in the thawing. Under any circumstance do not use a torch underneath. Believe it or not people have tried that and believe the torch thing falls in the category of "heat with any means possible".
In the future, I would winterize and leave the system drained when you are winter camping like this. You can use the toilet and flush with a gallon jug of water sitting nearby. Same with the sinks, just dump a little pink stuff before you close up and head home. You can use the RV in sub freezing weather just don't fill the plumbing system.