Another hypothesis ~ the comet didn't hit ~ that was just some loose junk on a far larger body that grazed the atmosphere.
It comes back periodically, but since it's on a quite eccentric orbit almost perpendicular to the plane of the ecliptic we see it as having an irregular orbit. So, 13,000 ybp, then about 6,000 ybp (accounting for Inkydo much better than the small body that hops from Earth orbit to Venus orbit and back over the ages), and maybe it simply left our system, or the inner planets after that.
A real machina ex deus!
Interesting that the extreme cold of the Younger
Dryas occured in a year or less. Scary.