My question involves a seatbelt ticket from the state of: WA

My wife was driving, I was sitting in the rear seat. Our car was stopped supposedly for speeding. The officer gave my wife a warning, but noticed that I did not have my seatbelt on (I did have it on when the car was moving). So unfortunately, I was issued a seatbelt ticket.

I know that WA has a Primary seatbelt law. However, in this case I think it was a secondary action. The officer's statement says "Defendant was the right rear passenger in a vehicle I stopped for speeding. Upon contact defendent never had his seatbelt on."

My question is: the officer's testimony does not state how speed was established (nor does my ticket have any mention of speed). Does this create a foundational issue upon which I can get the seatbelt ticket dismissed?