You're right, this thread will be buried on page 12 soon, but Steve could "stick" a longterm thread that stays near the top like some other important threads. Any attempt to motivate volunteers for any project requires an on-going information campaign of some sort. It would help if the folks at the store were supportive, maybe post a flyer.
Now if people dropped off their full wag bags instead of rocks, heck, there would be a huge wall there in no time.
[Do I really have to declare that I'm kidding? I guess I do, and I am.]