Hi all!

I have a C280 1999. A few weeks ago, when I was driving after a heavy rain, turn signals, windows/sunroof, and mirrors drivers stopped working (hazard lights worked though). I parked the car and found that fuse 7 is participating in all those circuits so I pulled it out (it wasn't broken) and put it back then -- surprisingly, all mentioned above started working. The same day I parked my car on the hill and saw water go out from the carpet on the rear passenger side by the gravitation, I'd say about an inch above the carpet. I cut off the carpet and wiped all the water I could.
The next day the real problem began -- when I put the key in the ignition, it wouldn't turn. The fob doesn't open the door/trunk remotely either. In the beginning, I was able to hear the "click" sound when I put the key in the ignition (the steering wheel gets unlocked) and even turn the key to start position a couple of times (no starter/engine sound, but seems like most of the electronics worked for a few seconds). Now it doesn't happen at all, absolute silence.
Next, I cut the carpet on the front passenger side too, and bent off a metal shield under the carpet -- a huge amount of water was there and my TCM was floating on the surface (off-topic: I am having trouble with the transmission when it's freezing outside, now it kind of makes sense).
I got a new TCM, but it didn't help. All fuses are good.
I thought maybe the key itself broke and called for a locksmith service. They checked the ignition and said that power doesn't go to the ignition switch, but the key itself is fine.
At last, some electronics still work -- hazard lights, low/high beam, interior light.

I fixed the cause though -- the windshield drain was clogged with debris, I cleaned it and now water goes where it should go.

I don't really know what to do, I think maybe the alarm or immobilizer system got damaged, but not sure where should I look for that.
All advice is very much appreciated. Thank you in advance!