Well, here's what I've found.
I pressurized the system and heated the water, and couldn't see any water leaking or accumulating anywhere. I let the water cool down and repeated the procedure - still no sign of a leak. YEAH!!! Everything was drying out. I went outside and carefully checked the seal between the heater and the sidewall of my trailer - there were voids! I guess with all the heavy rain we had this past weekend, some of the water found the void and invited itself inside my trailer. No rain today so I'm going to reseal the heater and hope for the best.
Once again, I want to thank everyone for the ideas.
Fingers crossed!