The same thing was happening locally for me here outside of Toronto, so I had a talk with a couple managers of the sports dept and told them I couldn't understand why they didn't order more on a regular basis since it always sold out immediately.
I suggested they'd sell a lot of .22 ammo since there weren't any other stores locally that were stocking much, if at all.
I had to keep after them since they seem to change managers every week or two, but now we have a very healthy supply of .22 ammo. I bought 4,ooo rounds the first big shipment that came in and there's regularly that amount of more now when I go in.
I've actually walked by the cabinet and didn't buy any a couple of times; if you can believe it.