Is there any part of this footage that can't be explained by a bit of matter stuck on the FLIR lens? Even it being apparently "cold" seems well explained by the dust/bug whatever casting a shadow onto the IR sensor array.
And the FLIR was tracking the target moving. If it was a piece of dust stuck on, it would have looked as if it were moving the same speed of the aircraft, wouldn't it?
The object had been observed before the pilot in the link flew. He was told to BOLO - be on the lookout - for this object.