Don't think I ever have from a supermarket, unless it was many, many years ago before such careful 'weeding' - used to get them every so often in our farm eggs though.
We had bantams as well as larger breeds, so yes, you're right, I'd forgotten, we got eggs in a number of different sizes. I forgot about shapes too - different shapes, depending on the chicken. My kids (who collected most of the eggs with their dad) were pretty good at telling which eggs came from which chickens just by their shape! (Our hens didn't have 'assigned' nests, so you could never tell which chicken laid which egg where!)