I completely agree with tsac
, even the smallest amount of moisture can affect your bb. Check the moisture indicators on the battery and the bb chassis.
If they show any amount of red - it will not be covered by warranty. It may be covered by insurance (if you have one).
Read this thread
Got Your BlackBerry Wet? - BlackBerryFAQ
I had a similar issue with 9700 after my wife used the phone in the rain. After drying the phone thoroughly I ended up with a similar issue. It was an easy fix, I bought a keyboard membrane on ebay (dirt cheap), dis-assembly instructions are available on youtube, and 15 min later I had a perfectly working phone!!!