I'm embarrassed that someone just went in to the work toilet straight after me
Do you think this person judged you?
I was able to find him on Facebook through face-recognition software. He only has six friends so he probably doesn't relate to people anyway.
Don't you think your a little overconcerned over people's opinion of you?  I understand feeling a little embarrassed about the bathroom issue, but it's not exactly anything you have control over.
I guess you are right. I shouldn't care so much.
I am glad that you realize that you were being too anxious. People expect people to use the bathroom  in the manner expected so most people won't judge you for that.