The Atwood?s put in a 2007 Fleetwood products definately do not have an anode. In fact they only use a nylon threaded plug, for a reason as you have discovered. But yours may have been replaced at some point with a different model. What are the model and serial numbers on the WH?
There may be a new tank or water heater in your future. Once you figure out how to disconnect the water/gas/110v/12v connections it?s a fairly straightforward process to remove it. Mine was. PITA because it?s under the washer/dryer with very limited access to the back of the WH. I replaced the heater element and mixing valve while I had it out just because.