Great writing here. Totally interesting.
I know how you might have thought thinking that no one saw you. I have been there. :)
I once had this bad experience at the gym.
It was the fall of 2006. I was still in College and decided to work out at the school rec center. It was a Monday because MNF was on. I wanted to get on a treadmill where the TV that was showing the game was directly in front of me. After waiting a few minutes, I got a treadmill that was about 3 treadmills to the right of the TV.
So I start running and about 3 miles in, I fell off of the treadmill. This was due to me trying to watch the football game a few TV screens over. One foot was on the track, the other foot was on the plastic side area. It was really embarrasing since the whole place was packed.
Everyone around me asked if I was ok. I immediately went to the restroom and call it a night. I looked down on my shin and noticed I was bleeding. I use my towel to wipe the blood off, the cut wasn't just a normal scrape...I could see my bone. I didn't feel any pain. I never noticed this but where your shin and skin are, there isn't much meat/muscle there.
Went to the ER, got 7 stitches. The doctor that stitched me up made a few jokes about losing to a treadmill then told me treadmill accidents are very common. I wasn't sure if he was trying to make me feel better or if the was being serious.

But in all these its natural to over analyse and feel bad, but dont let one day cause you another one. Great post @adsactly