Steal the cap next time. Problem solved!

That's sorta my point... On the grand scheme of things. "Ms." was popularized in the 70's as an alternative the "Miss" and "Mrs.," which indicate married status. It is the equivalent of "Mr." which does not indicate whether the man is married. Lately, I've been opening up myself more to, and becoming more aware of, gender identity issues. This lil incident, btw, included a quick shot of an "I know she didn't just me that but I sorta can't argue it cuz she's got me, at least on a bio level" expression from the cap-owner. It was THAT brief glance that spurred my thinking. So now in my head I am like, "Geez, sorry! What's the proper title for people who are so ambiguous with their gender?" What do I say without offending anyone if I get it wrong or right and on which level? Ergo the FORMAL "gender neutral" salutation question. Dude! Yo! and Hey, You! are not appropriate in all situations. Further btw: As a former tomboy (5-11 years old) I was questioned all the time: Are you a little boy? Or a little girl? While it was a badge of honor then, it would irritate me now... Back to the stream of thought: In hindsight, I realize I could have simple said, "Excuse me..." but in the moment the first word out of my mouth was "Miss." No biggie, I guess. But the concept fascinates me and I thought some discussion might come of it... Like the old joke tho: I'm a frayed knot."

I don't think this is the kind of thing you can generalize, since people have their own preferences. I would avoid using sir or ma'am (and "miss" is just not in my vocabulary) if at all possible, and ask what title they prefer if you really have to use a title.