I took your post that was flagged, lisagrace, and put it in Word. Ran the spelling/grammar check, found in the Tools, top menu bar pull down, and copied and pasted your post into a blank document. What it showed in red was didn't, the red being the missing apostrophe in the original post.
I have to admit, even as a paper grader in graduate school (I was a teaching assistant for an Art Historian from Harvard [picky]), and then 15 years of teaching in higher ed, I did not catch the misstep. Sometimes it is hard to be precise when we are feeling so imprecise, myself included on many days.
Welcome to the forum. There are wonderful and supportive people here. Many of us have been flagged. Try not to take it too personally. I hope you will find what you need here. (((Hugs))) And a shout out to (((((Srain))))) for the idea for using Word!!!