Talk to a couple people last night. The only place they knew that had firearm storage besides the WSU police was Diamondback Range in Lewiston. A little far to have to retrieve your firearm. It is in Idaho though so you wouldn't be subject to 594.
Here's the info from the WSU police website on gun checks:
WSUPD offers a safe place for you to store your firearm/s while you are on campus. Whether you live on campus or are just going to class, we will store your weapons, free of charge.
The gun check window is located on the south side of the Public Safety Building and can be access 24 hours a day. There you will see a call box which connects directly to our dispatch center. When using the call box, press the button and wait for a dispatcher to answer. You will be asked a couple of questions and then an officer will be dispatched to assist you.
Rules of a Gun Check:
All weapons must be unloaded
If you have your firearm in a locked case, make sure and bring the key with you so the officer can verify the serial number
Your firearm does not need to be in a case to be left at WSUPD
You may store as many firearms as you would like
We DO NOT store ammunition
You may check your firearm in and out as many times as you would like
If you have any questions regarding the gun check procedure feel free to call WSUPD at 509-335-8548 before bringing your firearm on campus.