My Rx got a little wet.
First of all, let me qualify this by saying that I work with electronic instruments in ocean water all the time.... I think I have a 'clue' as to what might work and what might not.
Even though this isn't salt water, the puddle you dunked this into has mud and other contaminants in it. These contamints might be shorting out the traces or components on your rx board. This is probably what might be causing your problem.
DO NOT apply power under any circumstances to 'see if it's fixed'. You could be doing further damage.
I'd clean the board as best I could (you can get distilled water from the drug store to rinse it as clean as possible), then send the rx off to a repair facility. I would consider the rx very unsafe until professionals checked it out. Tell them exactly what happened, and what you did to minimize damage.
There are a lot of places for moisture (and contaminants) to hide inside a rx under the components and inside tuning slugs, etc. Remember, it's not the water that causes problems, it's the contaminants in the water. PURE water is almost an insulator...
Yes, it's possible that the rx could dry out and not cause you any more problems. That is, until the next humid day. Then, it's a crap shoot.
Take the circuit board out of the case. Take a CLEAN toothbrush (used is OK, with soft bristles) and run some water over the printed circuit side. Brush it with the brush to clean it. If you got contaminants on any of the lands, it could be conductive and causing some of your problems.
I'd hold off on rinshing the component side only because the components are so close together, you might do more damage than good. And, if there are any hollow components (tuning slugs, etc) that were dry before, you'd get water in them now.
If you had access to PURE water (not tap water) you could try using that for rinsing the board off. You might find distilled water at the drug store. Rinse the board and let it dry.
What you are trying to do is to flush anything that might be corrosive off the board. I strongly recommend that you do NOT stop here and try to fly with this rx. You still do NOT want to apply power. You could still smoke the rx.
At this point, you might want to send the rx off to a repair facility with a description of what happened and what you did.
Only as a suggestion, I have sent some of my receivers to Radio South after a crash for a checkout. They're at radiosouthrc.com and I've been happy with my dealings with them. They could give you an estimate (I'm guessing that they'd charge you a diagnosis fee), but you might get your receiver back in like-new condition for less than the cost of a new one. And they thoroughly test the rx while they're repairing it.
Just my thoughts..
Bob