I would have thought you would have seen your filter open at that time.
Those cowl covers let a lot of leaves slip in and with the filter open like that, quite possible they ended up in the evap drain pan clogging the drain.
I've seen evaporators completely covered in old leaves and debris from over the years.

https://cimg8.ibsrv.net/gimg/www.che...3ccfe4ee32.jpg
https://cimg2.ibsrv.net/gimg/www.che...0298312741.jpg
https://cimg4.ibsrv.net/gimg/www.che...558b7e27f0.jpg

I pulled back the butyl patch carefully...
https://cimg2.ibsrv.net/gimg/www.che...c84d60243b.jpg
Filter looks installed pretty well for my first attempt!
https://cimg4.ibsrv.net/gimg/www.che...24ee37c6d5.jpg
Under the butyl patch looks pretty good too. It was difficult for me to get in there good with the hood support (whatever it's called I'm too tired to look it up) and my upper torso. I got parts that inhibit me getting in there good.


https://cimg1.ibsrv.net/gimg/www.che...ce6e2a8dea.jpg
I was pretty excited when I found the two rubbers screws that hold part of the cowl to the windshield trim. .
https://cimg9.ibsrv.net/gimg/www.che...e37ae13576.jpg
I also picked up replacement windshield wiper arms. My were messed up bad and was only getting them to work by putting some steel wool on the bolt and tightening them down. Most places wanted $50.00 apiece for them. The guy at the junkyard threw them in for free. I think the cowl looks pretty clean overall!

Nice work! And now the rain test!

Yesterday I bought the A/C Pro Vent & Duct Cleaner that Don showed. It is cycling right now. I still tried putting a different trim line up the drain tube...no real success.

If by chance y'all don't think I did this...
https://cimg1.ibsrv.net/gimg/www.che...e172683157.jpg
Thank goodness for Zep Orange Heavy-Duty Hand Cleaner. I remember dad cleaning up with Goop. That stuff stunk in my opinion.