I just bought 4 peace dollars from my local dealer and found a 1928. Most have been 1922 and 1923. I guess that is because there were many produced in those years and also because dealers and collectors surely don't sell key dates as junk. The 1928 date looks a lot like 1923 so maybe it just got skipped. Great find for $28!
If it was in with scrap coins, it's most likely because the dealer thought it was an altered 1928-S. It's possible that you're right and he was wrong, but that's not the most likely outcome...
I've gone through my mother's friend's collection he inherited and I think you are right about the dates looking alike. I seriously had to double back and check all 43 1923 peace dollars weren't 1928s
With the reverse looking like that it almost seems like it was in a belt buckle. Neverless an amazing find! congrats!
1,632,000 mintage isn't exactly common but I was excited to see a rarer date from the junk bin. With my budget I can't really expect much more. Sorry if I got your hopes up.
It is absolutely possible to pull a 28-P out of a junk bin, especially if heavily toned. No reason to bust on the OP for his being an S. He is pleased and that is what really matters.