Hello Lauren, we as a gender (trans) have a strange set of notions, getting upset when someone uses bad english around us, I am actually more offended when someone curses. Of course I have by accident misgendered someone, others have misgendered me no matter how I am presenting. I have seen other people both cis and trans alike misgender each other, whether the other are cis or not. When in male mode people used she/he/Miss at me once in a while, and in female mode the opposite is true I had people use he/him/Sir. When someone calls my very feminine wife (5’5″ with plenty of curves) a sir she does not batt an eye.
I am fairly sure It happens everyday because people usually do not pay attention, they are too wrapped up in whatever they are doing, and only took a super quick glance or are using peripherals to ID your presence. Unfortunately as a culture we Americans care too much about our selves and to blame someone who was raised as a self centered individual is almost as self centered as the person you are blaming. So I think you did the right thing, blow it off as just another human who was not paying attention.
Now on the other hand if someone has gone out of their way to misgender you, I have had this happen as well. This is where your grace and poise comes in. Depending on you upbringing is how you handle when someone is being deliberately rude to you. If you are a typical male a punch on the nose might be appropriate, of course so is a night in the slammer. If you are Royalty a witty blow or “off or off with his head” to underlings might work. Do whatever works best for you. I tend to just simply ignore them as well and treat same as people not paying attention, it is their misfortune that they are rude not mine. More than likely a person who is verbally wanting to fight you is scared of you, and sees are part of them selfs in you, this scars them deep down thus they pick the fight vs flight response. And to fight them is the uncivilized thing to do also it is the masculine thing to do. Plus breaking a nail is always a pain in the rump.