You've made a point about thermal signatures from caves that I have pondered upon, recently. It makes a lot of sense. Thanks.
But to add, American military personnel have many...many...many... different ways of dealing with armed terrorists who maybe cowering in caves:

(1) Like the leathernecks in WWII
at Saipan, Iwo Jima, Okinawa, you can
use flamethrowers [I wonder if the
younger generation of Americans would tolerate such an unpleasant way of dealing with evil people?].
(2) You Americans are great at improvisation. EXAMPLE: To keep civvies from being torched in Afghan caves by mistake you can fit two fiber-optic cables into, say, 100 feet of BX electrical wirecasing, and snake the tubular casing deep into a cave without risking American lives.
Illuminate the inside of the cave with a flare, searchlight or laserlight
beaming down of the fiberoptic cables
And a TV imager will let you know
"what or who is residing in the cave?"
If it's a couple of Talibani, or
terrorist recruits, cowering inside
with their hand-grenades and AK-47's,
well...You can fill in the details.

(3) If that doesn't work, there's
a unique UAV invented, that has been tested recently. It's the smallest UAV
ever flown [smaller than a frisbee] according to "Guinness World Records";
and, radio or wire-controlled, it has the ability to flit about, even in the confines of a cave.
Oh, yes! It has been tested with a
miniature TV camera added [I suppose
a small AP explosive device can also
be inserted, too.

(4) Fuel-air bombs.
(5) Mininukes.
(6) Tracked or wheeled, cable or radio-controled robotic devices similar to those used by "BOMB SQUADS" around the world.
[7] etc...

Jacob