I've been here before. In WA this can be a bitch.
Motor on down to the DMV, in person, and tell them the situation. In my experience they will attempt to notify previous owner that someone is trying to amend their title, since they technically own the bike and never "sold" it. Previous owner gets a said amount of time to contest it, and if nothing you'll get a new title.
I've heard some horror stories about going out of state for replacement titles, and wouldn't recommend that. If you want a clean title, you're going to have to jump through the hoops.
BUT. I would first call your local police department and give them the vin and license number, if it has one, and have them run it to see if it's flagged as stolen or whatever. Tell them it was left on your property by a previous tenant or whatever, you can't contact them and need a replacement title so you can legally deal with it. If it is flagged hot, which it sounds like it won't be, this can save you a huge amount of hassle. In some instances, they can dig up the previous owners info and provide it to you. Worth a try.
Current toys = 2001 Honda 400ex, 1974 Honda MT250 Elsinore, 1985 Honda NG50 Gyro S
Past toys = 1986 Kawasaki KX80, 1972 Yamaha CT2, 1977 Honda FL250 Odyssey, 1983 Yamaha YZ250/24Y, 1977 Yamaha IT400, 1982 Yamaha YZ490, 1983 Yamaha XJ750MK Midnight Maxim, 1975 Suzuki T500 Titan, 1982 Suzuki GS850GT, 1974 Kawasaki KZ400