I always thought that it was Mrs. = missus, Ms. = miz, at least that’s how I would say them, but I now realize that a) that’s plainly incorrect and b) I’ve never actually ever seen them non-abbreviated.

If an abbreviation is never expanded, is it still an abbreviation? Personally I think it isn’t; I advocate for condensing i.e./e.g. to simply ie and eg, though this is a minority opinion.