Here's something odd that I wanted to just put out there.
Twice this week, I picked out another person's tree and decided to do a bit of work on it. I do that sometimes. I get bored and pick a random person who's posted on the wikitree board and see what I can do for their tree. Mostly it's just adding sources and stuff, but occasionally I do a bit more. Once and a while I'll add missing siblings, source them and then abandon the profile for the relative to pick up.
Sometimes people who match my dna on gedmatch, I work on theirs, in hopes of digging up the connection between our trees.
But twice this week, I found that profiles for close relations already existed and had been created by other people. I was just a matter of connecting the trees and adding the sources to back them up. One was today for a tree I picked literally at random from the message board. I was able to connect X person with the profile of Y, who was his mother.
Just goes to show you, that a missing ancestor may already be out there. But finding two connections, in one week at trees, I picked pretty much at random was a bit strange.