I don't know if you still need to know this, since the thread is a couple months old, or if it will be helpful to anyone, but I had this exact same problem (except it was the condensation from a Subway cup), and recently came across an interesting solution.
There is a Trivia game you can download for free from the Marketplace called "Disney_Quiz" (screenshots included so you can make sure its the right one.) that will automatically turn the volume all the way up for you to 30/30.
I didn't do anything remotely special to make the volume turn up auto, I just fiddled a bit with the buttons in the game, clicked this here, clicked that there, tapped the volume down button on the phone a bunch of times, and eventually the volume restores itself to 30/30.
Hope this was of help.
P.S. The game itself sucks, but whenever I accidently turn my phone to silent and the volume drops to 0... it's nice to know I can still turn it back up.