Turns out I was washing my dirt screen wrong, a guy at the Tucson artifact show set me straight
I've been sifting dirt from a creek site near my place for about a year and kept losing tiny flakes through the mesh. Last Saturday at the artifact show in Tucson, a guy with a table full of points told me to soak the screen in a bucket first and swirl it instead of hosing it down, so the small stuff settles instead of washing off. Tried it Sunday on the same gravel and pulled out 11 flakes I would've missed, including a tiny piece of worked chert about the size of a pea. Seems so obvious now. Has anyone else had a simple fix like this that changed how they dig?