The very reason years ago we started doing crazy things during PDI. We take all panels off, drawers out, and anything else to access connections and piping during water tests. We've even pulled underbelly down before. Fill tub, or shower pan with water by plugging drain with tape or whatever and check 30 min later (checking drain seal), and on the list goes. I've had shower connections leak inside a wall with no access panel (added one), black tank flush siphon valve leak in wall (deleted), WH leaks and on the list goes, all on previous and more expensive rigs. Do you have the enclosed underbelly? Sounds like you don't. Somehow you'll probably have get the darco off the bottom (The stuff holds water), get the wet insulation out, and maybe if you're lucky you can run a dehumidifier and get everything dried up. Just my uneducated observations without actually looking at it. Could've been a lot worse really.
John and Rebecca Dickson
Emma-8 / Little John-5 / Iva-1+
2013 Ford F-350 Lariat FX4, CC LB PSD, DRW
2015 Jayco Jay Flight 28BHBE (#8)