I would have paid the toll if only I knew how.
I asked the hotel front desk the same night and I was told there is no way to pay on site. The toll charge will be mailed to the car registrant. I think this is very tourist unfriendly practice.
Even if I knew about the short term account, I did not honestly think I would sign up. Reason being I had no idea about a toll road in Seattle and had no intention to use one when I visited last time.
This was a very expensive toll, imho.