Version 0.7.584 - My Colonist keep vanishing?!

[Dafaq1029]

Version 0.7.584

Every now and then a enemy raid, siege, or drop pod attack will come my way. Nothing new really. So I'm fighting off these raiders, and I finally took out about half of them, when a notification comes up on my screen that says "Raiders decided to capture who they can & leave". Well, I won't let them. So, one of the raiders grabs my colonist. *pew pew pew* and the raider goes down. But, my colonist can't be found. I can still find them on my overview screen. It still says they are in the exact spot where they where dropped, but they are no where to be found.

This has happened to me about twice so far. I would also like to point out that the "Colonist needs rescue" notification does not pop up either. It seems to happen often when they are dropped near sandbags.

Has anyone else gotten this glitch/bug? If so, do you know how to solve this problem?

[elStrages]

Alpha 0.8657
I know this is an alpha 7 bug but I just came across it again in alpha 8.
Killing escaping enemy with captured colonist causes the colonist to disappear.