First things first: it sounds like you might be a newbie. That is great -- please ask lots of questions. We old-timers like to answer them and to help you avoid the mistakes we have already made! (Plus it gives us something to do while hiding at home to avoid the virus.)
Let's see if we can narrow this down. First, the anode rod is a thing that sticks into the tank to prevent corrosion. Depending on which model water heater you have, there is probably a big hex head on the outside end of your rod. It sounds like you have not removed it recently (otherwise you'd know where it is). When you get a chance, you should check it to make sure it's not corroded. But since you have not removed it, the chances are good that it is not the source of this leak!
By the way, here is a photo of a typical Suburban water heater -- the hex fitting for the anode rod is in the bottom center of the photo:
Click For Full-Size Image.
Second, there is a pressure relief valve -- it usually has a lever that hangs down from a brass fitting toward the top of the tank -- in the photo, the valve is blue.
So now the questions -- when you said you saw it leaking out the back, do you mean when you were outside the trailer? How much was leaking? Were you using the hot water at the time?
When you said the water was laying under the tank, do you mean inside the trailer? Or do you mean on the little shelf under the big brass burner?
The answers to those questions will help us narrow down what is going on!
Hang in there.