Because I'm at work, I don't have the other key to be able to determine if it's a system issue or the battery in the key is just dead.

Since the panic button is also dead, is that a good indicator that the battery on the key is simply dead and it's not a car issue?

(Just concerned after last night's horrific downpour..if something got water in it and is now defective..)

 

This is a tough one, as it could be any one of those that you mentioned.

you really need to test each devices battery; the key fob and the car's battery.
Hopefully your water drains are clear, and water did not get into the fuse box.