I'm assuming by pushed up you mean higher up the beach (not draining back as quickly).
My confusion comes from being told an east wind pushes the surf up, meaning it stands the waves up vertically, causing them to crash down on the beach with much more force, causing the clams to lay low.

Is this true about an east wind? Intuitively, I would think the opposite, that a wind blowing in from offshore would cause the surf to hit the beach with greater force.

One final question, is it true that once the tide has turned the clams wont show? Is it impossible to dig a limit starting a half-hour after the low?