Happens.
The first thing one should do is not to turn it on right away. Then dry it out, preferably opened. Some do survive this without problems.
Another lucky owner had it still responding only on the usb connection, and revived it by changing the battery. Slim chance, but check if yours responds to cable.
Other strategies are:
b) Buy a new one and pretend it never happend
c) Pretend it works
