I didn't look for 16 gauge at any of those stores, as I'm still working off a pallet of 16 gauge English 2 1/2" loads I bought in the mid 1990s. Never thought I'd say it, but, I wish I had bought two pallets.
Dick's in Bloomington, MN didn't have a single round of 28 gauge the last time I was there, either. I think that is the flagship store.
The only 28 gauge ammunition my gun club, Metro, in Blaine has, is an 8 shot loading of Rio. They had, at one time, several different loads of Winchester AAs in 28, but, those days are sadly gone.


Best,
Ted