Semi-truck hit-and-run; help with plate lookup?

Hello all,

My (regular pickup) truck was involved in a hit-and-run. A kind person in the neighborhood witnessed the incident and left a note, indicating that it was a semi-truck that hit me. They also provided the plate number, which has a small "ST" on the end of a six-digit plate. I'm assuming "ST" stands for semi-truck? I am located in Seattle, Washington State.

Would anyone be able to help me look-up the company or owner of the semi? I have reported this to the police, but am still waiting for any follow-up.

I was a warehouse manager for years and have always had the best interactions with the truckers I worked with. In general, truck drivers are some of the most upstanding gentlemen I've ever met. I'm hoping that this carries over onto this forum, as well. Thanks for any and all help!