Leaving it wet as long as you did, especially with dirty water, started a lot of corrosion going. (Also there are microorganisms in lake water that will eat various things in your phone, like the conformal coating on the printed circuit.) This won't help you, but if you get a phone wet, the first thing you do is remove the battery as you toss it into a bowl of rubbing alcohol, then swish it madly so that the alcohol gets to every spot any water might have touched. You should already have a good relationship with your local cellphone tech. Bring the bowl, alcohol and all, to the tech and let him take it from there. Alcohol is hygroscopic - it absorbs the water. Rice may absorb almost all the water, but the chemicals remain - and do the damage. H2O doesn't damage a phone, the stuff dissolved in it and living in it does.
A few seconds with power running through the phone (if the battery is in the phone, current is running through it) and electrolysis starts setting in. That's really all the time you have.
Your phone, at this point, is just going to get worse and worse, as more things start to fail. Sorry.