I wouldn’t worry about it. You’re not old at this age. It can be a lot of things that made them say that. Like maybe you command respect just by your presence or the way you walk is sensual etc. Thinking about it can make you crazy. Someone called me ma’am the other day and I freaked out. But now I realize that people don’t really say miss anymore to even teens. From the time people are 20-30, we all look about the same, there are no significant changes. Don’t listen to them. You are not old.