They didn't leave a note? In all seriousness, how would we know where they went? It's your tank. Do you have tankmates in with them that could eat or kill them? Are there hiding places where they could be tucked away?
Rams do tend to be sensitive and it sounds like they were already in rough shape. Are you sure they didn't die and get stuck somewhere in the tank?
If they pull through this, please realize that rams need clean and fairly warm water to thrive. Keep up with your water changes and don't let your temperature drop too far below 85F. That will also prevent future ich outbreaks.
