If it is in fact a result of the fob going through the washer, there could be one of two things
happening. Either something is creating a bridge on the circuit board, or something is
physically sticking the button for the alarm. First, try to use the alarm button. If you press
the button and it sticks or wont press back out when you release, that's likely your issue.
If everything seems totally normal there, it's probably a bit of debris or a film of soap suds,
etc creating a bridge to close the circuit on the board inside.
Either way, you're going to want to open the fob up and give all the bits a gentle cleaning
with isopropyl alcohol. Dampen a lens cloth or cotton swab with the isopropyl alcohol and
gently rub down all the surfaces you can access. This will clear any detergent residue or
other film and gunk from the surface of the board to stop it from bridging, and it should
also address anything which would be making the button stick.