I have hitchhiked out of that same I-90 intersection many times--mostly in 1986 and 1987. There used to be a Christian hostel in Ellensburg.
One time this lady pulled up in a Delorean (the fancy, stainless steel car with the gull-wing doors) at that same intersection. She gave me a ride east on I-90 to a small town near the Columbia River.
