A couple of days with one "wand" of the shop vacuum shoved under the carpet (hard to pry up: it's shaped to fit the space), running the vacuum on "blow," seems to have done it.

You could take the passenger side carpet out, but you are in California and the sun will come out and help. Once the pad is dry, put it in the trunk until the floor carpet is dry.

When your neighbor blew out the drain, did you notice any debris on the driveway? I only ask because if the fresh air intake, in front of the windshield, is full of crud, the water may have gone through the ducting and out near the cabin filter.
--
Keeping it running is better than buying new