Water leak on passenger rear floorboard, what could it be?

[Theos92VR4]

Ive been dealing with this issue for a little bit now! The rear passenger floor mat, and carpet is always wet. I have tried to see if I can find any drips while its raining, but i never see anything. the floor is SOAKED, to the point where I can shop vac out water from it. Its ONLY the rear passenger side, no other parts of the car are even remotely damp. Ive checked all the other spots. I even sprayed water on the car and found nothing!

Things Ive tried/found out
Cleaned all the drains
Siliconed the entire passenger side rain channel (the rubber piece was loose)
Checked window for leaks - Nothing
Checked door seal for leaks- Nothing
Checked headliner for wetness- Nothing
Checked floorboards for rot/holes - None

Im really stumped here! My car is starting to smell so I would like to fix this problem asap! Has anyone else had an issue with this? thanks in advance

[EsperHamid]

if it doesn't get too cold in your area, delete the heater core, it is a little of a PITA job but it can be done. I am actually in the process of doing it.

also it could be the front windshield, which needs a shop to do it

[Stoner51]

If you are using the ac a lot; the drain hose may have fallen off.

It comes out of the middle black box and runs through the firewall.

steve

[oyajicool]

maybe a rust hole on the floor of that section......

right rear wheel well????