Uh oh.. a strange AF 1150 problem?

There probably is a loose water connection fitting. Check them all, everywhere. Worse case would be a leaking tank.

Since the camper was under a roof, I think it is not very likely that the "source" is anywhere on the roof or high up.

Was the water heater drained? If not, it is possible that that some connection on the water heater failed (the heater is on the driver's sid / front as far as I can see on AF1150 pics). That happens somewhat frequently, and usually not a huge leak. Should be visible when inspecting the connections of the water heater. Same could be possible for the water pump, which may or may not be in the same general area on that camper.

On that side, there is also one access door and the lower refrigerator grille. Both can be good sources for leaks, where the water would eventually end up in the floor. In all cases, you should be able to find traces of moisture in the camper wing and the way down. If neccessary, you could test with a garden hose and see if you find any intrusion.

But as KKeller14k has said ... any opening can be a leak.

IMO it is not very likely that any rain got into the truck bed and from there into the floor. The camper overhang to the sides is big, and I have never found water in the bed - even though my rig is sitting outside in the weather.

Lets get real...any moisture coming out of any RV, regardless, is a fail of some kind. You got to find this fail and source of water leak right away...don't put it off....you need to find it yesterday. It could be as simple as a bad seal on a marker light....or trim molding. Look hard at all the cutouts on that side....it could be anything, from windows to cargo doors....good luck.

It's the lowest drivers side corner at the front. I spoke with Northwood and they advised me to fill all the tanks and check for leaks. If no water spotted then the wind may have pushed rain into the truck bed and perhaps it didn't drain well. I'll check all this and the drain holes tomorrow.

I don't really understand which corner is leaking. Is it at one of the lower front corners, near the camper floor?
Was the truck bed dry in the general area?
Was the side that leaked exposed to the weather under the carport?
With your description, it could be anything from harmless to major problem...

First all TC manufacturers advise keeping the front higher when operating the jacks.
All flat roofs sag a bit under its own weigh, or the weight of AC and water likes to puddle in low spot to drain with camper tilt.
That could be even condensation water.