Unity,
My suggestion is to borrow a boat and float from Big Eddy to Sultan ASAP. This is about 6 miles, mostly class I, can probably be done in a kayak in a coupla hours. Alternative is to float only to Gold Bar which is less than half way. You can access the river for a kayak takeout at Goldbar by crossing the railroad tracks at the little park just east of the park and ride. Somebody along the river is going to find that boat, if its still floating, and not everyone is honest enough to look for the original owner.
Good Luck!