It happens, less as time goes on, but paradoxically you are most likely to be misgendered and treated with transphobia when you are 1) around a mixture of LGBT and cis/straight people, and 2) one of those people has reached their limit of how much "queerness" they can tolerate before they have to say or do something offensive, rude, and stupid. I was enjoying a nice lunch at a nice restaurant in downtown DURING PRIDE, when our waitperson rudely and stupidly insisted on misgendering my boyfriend, even after being corrected twice. She also gave us abysmal service. There were at least two gay couples visible in the restaurant at the time, and she clearly had lost it. Management was notified in person and online.
I know it can really throw you emotionally when it happens, but really it is a reflection on the character and ugliness of the person who is hating, not a reflection of the character and beauty of the person who is on the receiving end. With experience you get better at letting ignorant people's demonstrations and remonstrations land on deaf ears. Or you can choose to educate, escalate, or just escape. *hugs*