See my response to thenewgreen; ask yourself, if you were trying to make small talk, why of all things would you ask a question of a woman which seeks to determine her relationship to the man she's with, as opposed to, I don't know, the weather? The holidays? How much you like their car, or chocolate, or anything else but?
Frankly I'm in the middle of it and don't know what to think about it. I suspect men are hit on less than women. I think when you're not hit on a lot, it's much harder to recognize and also much easier to doubt another person's claim that they were getting hit on. Honestly, I wouldn't be going around talking about how this dude possibly hit on me at Goodwill, in any capacity, except for my brother - first, obviously, his involvement. But beyond that, AKA a large part of why I'm confident in "He was hitting on me" territory, is because my brother was there, an observer who wasn't a participant in the conversation but saw the whole thing, and he independently came to the same conclusion about the guy's behavior as I did. I didn't get into the car and say, "Aw man, that guy just hit on me, did you see that??" As for whether I'm mistaken - I don't think it matters as much as you think, what his intention was. The road to hell is paved with good ones. If I came up to you and got handsy with you because "You looked like you needed a hug and I wanted to make you feel better," that doesn't give me a free pass on intruding your personal space and touching you if you don't want me to do that. You can always say I didn't intend to do that; it's real easy, in fact, especially afterwards. Kind of like "I'm sorry." You can say it all you want. It doesn't change your actions or the impact of them.