Cool. But yes. And just to help you out here, as you seem to be struggling, if the press know, then a handful of people knowing is unlikely. If only a handful of people know, then the press can't know and any reference to UKSF22 can't be trusted as cited source on these forums.
So which is it?
I mean I know people have levelled similar comments at me but if you are employed in a position to know then someone really should be having a word with your SC (or equivalent depending on service) and if you aren't but do known then you probably shouldn't be posting anything too specific.
I'm guessing that, also police thermal cameras tend to look at relatively large areas with low detail (so it would need to be a large hot source) or small area areas with higher detail in which case you're even more likely to miss it.
The drone's only real heat output will be it's motors and they're far smaller than what the thermal cameras police copters are equipped with are normally meant to be looking at (humans, motorbikes, cars etc).
Wonder if it is possible to locate/track via a mixture of sound positioning - the noise they make is fairly distinct and some kind of optics.