We can ask Mookie, I'm pretty sure you've microagressed him pretty hard.
I can't think of an incident where I have. But I probably have. Fag or not, I'm a white male. I'm sure my very existence is a microagression.
Seriously, though, yours wasn't really a microagression unless you were ignoring the woman because she was a woman. If you were ignoring her because you had been dealing with the old fellow and had just continued that, it may have been a little unintentionally rude, but it wasn't a microgression. At least not to my mind. But who knows? Most of the concept of microagressions is booshee.
I think a lot of what is referred to as 'microaggression' is BS and yes, one can make an argument that the reason they are a 'thing' is so that people who aren't macroaggressed against can say 'me too!' When most of the problems in your life are solved, it's the little things that are left that will start to irritate you. Often the very concept of microaggression relies on mind-reading, because they rely on the person feeling microaggressed against interpreting the actions of the aggressor to determine his/her beliefs or thought process.
I'll give an example of behavior I exhibit, which, if the person experiencing my behavior could observe enough of it, they might guess I am microaggressing (or perhaps not!)
I work in a 5-story building, on the 4th floor. Sometimes I share an elevator from the 1st story up. If I get in the elevator and the other person pushes '2', I just push 4 and wait. If the other person pushes '3' or '5', I ride with them to their floor and walk 1 flight of stairs up or down to mine. That is, I don't want to wait while the elevator stops at 3, and I don't want to make someone else wait at 4 while they are on their way to 5. If they push '2' I'm willing to wait for the stop to avoid 2 flights of stairs. (Honestly, sometimes I walk up all 4, but if I go to the elevator, the above is my recipe)
The exception is when I am alone with a woman. Then I press '4' instead of riding with her to her floor, as I worry that she might perceive that as 'creepy' since she can't know the reason I do it unless I explain myself, which I would rather not do. It's a small office building, and a woman who figures out that I have treated her differently than others might consider it sexist (and maybe it is!) particularly if she doesn't know my full reasoning (and how could she?)