Draw Adjudication Mistake

My opponent was very unlucky here as the system wrongly gave me a draw.

I had a clear material lead but only had seconds left, so was sacrificing my pieces for pawns to try and get to a drawn K+B (him) v K (me) position and avoid losing on time.

However, my opponent was wise to my plan and cleverly ignored my last pawn sacrifice, leaving the final position as below when I timed out.

I expected my opponent to be rewarded for this good play with a win - there's clearly a checkmate for him in the final position, however unlikely it may be that I would cooperate with it. But the system adjudicated it as a draw. Unfair to my opponent! 

I think FIDE rules and USCF rules differ somehow. Those positions might be considered a draw under USCF rules, but I am not sure...

what's the rule in cases when one runs out on time ? is it that the other player can make moves for both sides and if he can show to checkmate the king of the side whose time has elapsed he wins? 

This website follows USCF rules in this situation.

K+B is considered insufficient material as a checkmate cannot be forced. So correct result is a draw.

FIDE rules are different where the arbiter only needs to consider if a theoretical checkmate would be possible (had the game continued) "by any possible series of legal moves"

Thanks Lagomorph - clears things up a bit but feels like USCF rules ("insufficient losing chances") are inconsistently applied: I've lost several times despite being 1 or 2 moves from mate.

For example, I think the diagram below with white to move would be a loss on chess.com for white if they timed out?

I guess it's easier in a tournament with a human adjudicator rather than using a simple rule-of-thumb based on material...

what would be the result in above position in fide tournament?

yes but if white timed out?

If white times out before moving, FIDE rules say it is a draw.