Sonja shuttle for the clark fork. Maybe $25. If you're there in the main season then hitching a ride back from tarkio usually isn't too bad. Cyr to tarkio is the most common stretch, continue to forest grove for a bit more beautiful gorge
Edit- july- just hitch a ride back up to cyr from tarkio. If you want to go to FG hire the shuttle.
I am a river, babe - I've got plenty of time, I don't know where I'm going, I'm just following the lines..... - "We are water" by Shaye