Powered Stainz and tender, should both pickup, and both run independently..
On the tender:
Check the skates have not got stuck. - They should spring back when pushed up.
Clean the tread/tyres of the wheels, where they run on the track.
Clean the rear face of the wheels, where the carbon-brushes rub.
Check the brushes have not worn a lip on the side, and are not moving freely to press on the rear of the wheels.
Tender should now run on its own..
You have cleaned your track, since it got wet, I assume? - I believe you can get something called a 'Swiffer' in the States? - A pad on a long handle, basically.. With a little Isopropyl Alcohol, this will remove the black 'gunge' from the track, without bending.
Your loco may (if you are very lucky) still just be wet inside..
I would leave it somewhere warm and dry for five days, then try it again. - ONLY have the loco on the track when you try it.
Oh! The cleaning from above may help, but it does look like the decoder has been damaged, sorry.
PhilP.