1. What the circumstances were + 2. What happened.
So, In the way back this used to be a thing that could happen and acording to the wiki it still can happen. On day 6 I lost my colony but I liked the seed, I liked the map and I liked my little setup so decided rather than a reset I'd wait it out. we are now past day 306 nearly 5 hours play time and no body came. I believe the AI tried to give me extra people but they was all wild people who would need taming which.. you can't do without someone around to.. do it.
3. What you expected to happen.
I expected after some time had past (hopefully way less time than 5 hours irl) for someone to come and choose to settle the area again.
4. Steps we can follow to make the bug appear on our machine. This part is important! We need a set of steps which we can follow to get the same results you're seeing. Ideally you'll test these steps to make sure they work from scratch.
Start a new world with 100% of the world being formed. lose your last colonist, and simply wait to see if anyone comes.
5. Savegame file
unfortunately the save file would be larger than I can upload (16,909KB)