Yes Dolly Varden/bull trout are fall spawners (typically spawning from mid-September into Novembre) in this part of the world. Exact timing is dependent on stream temepratures. You fish probably disappeared becasue they moved downstream -not upstream. Many of our char are anadromous with them moving downstream and into the salt in late winter and early spring. The adult and sub adult fish (those over 14 inches) can enter the salt shortly after spawn or as late as mid-spring.