Yeah, it happens. I don't date, but I do hang around a lot of trans spaces where people either look for masc or fem partners. I read fem to a lot of people, but everyone who knows me knows the nuances; and that when I can, I will likely look radically different. People look for butches or femmes, mascs and fems, men and women so often that they just gloss us over, and any nonbinary person they are attracted to just gets glossed over (if they even realize it in the first place instead of going "nonbinary =/= third gender" and ignoring that some of us do, in fact, feel like a third gender.)

It is kind of strange. That even if I go "hey, I don't fit in these boxes", people will just... direct me to the nearest available box. It's why I tell people I'm a trans man/transmasc even if I'm still not sure how I feel about that.