I live in WA. Don't worry so much about the concealed part...Open Carry is just as legal as CC...That part is not a problem. Can your private employer restrict your carry on his/her/its private premisses, yes, but not in your car...However, you stated you take the bus.
So, now, what to do about your employer. My solution is: Talk to them about giving you a place where you can lock your weapon up after you come to work. Tell them you are afraid to ride the bus at night without some sort of personal protection, and that you are perfectly willing to go un-armed while at work, but not going to and from work. Don't just talk to HR,,, talk to the CEO if needed. Your request is not unreasonable, and if you are reasonable, most employers can be also. You could even volunteer to provide the lock box.
If they refuse to allow you to protect yourself coming and going from work, get it in writing...that way you can show that it was their reckless neglagent disregard for your safety in their refusing to allow you to protect yourself during your commute,,,that caused your problems, should you have any.
Unlike what others have stated here...In WA your employer can be liable for what happens to you from the time you leave for work, until you return safely home...under certain conditions. One of those conditions is just what I stated above.