I think I may have incorrectly addressed a tranny at the office - am I fricked?

For context, I work in a very large corporate office. At our cafeteria on the main level, there are 4 cash registers. 3 of the 4 are typically manned (or womanned) by the same people every morning during the breakfast hours.

One of the 3 people at the registers is very obviously trans. It has an Adam's apple and a clearly masculine voice, but dresses in feminine clothing and has a feminine hairstyle, as well as long nails and a perfume scent. I typically try to avoid this person when I get my morning omelette, but this time there was no line at his (her?) register and going to a different register would seem like I was deliberately avoiding.

I have a habit of saying "thank you, sir/ma'am" when I am thanking someone. This morning, after he/she checked me out, I said, "thank you, sir." Instead of saying "you're welcome," he/she looked at me with a very puzzled look and then looked away.

I very obviously oppressed this person by misusing pronouns and therefore created a hostile work environment. Should I start updating my resume and LinkedIn?