Flag fall as last piece is taken

[HLang]

Scenario: Rapidplay game. Black takes white's queen with the move ...Qxd1 then, before pressing her clock, points out that her own flag has fallen. In the position after ...Qxd1, white has a bare king.

My understanding is that a flag has fallen when it has been observed to have fallen. So:

Is it a draw because, in the position on the board at the time the flag fall was observed, white has a bare king?

Or is it a win on time for black because white didn't successfully complete the move that produced the bare king by pressing her clock with her flag still up (even though the move had been made before the flagfall was pointed out)?

And would it make a difference if someone had been watching and could say with certainty whether the flag fell before or after ...Qxd1 was played?

(The only other time something a bit like this has come up, the move played was checkmate, which immediately ends the game unless the flag was observed to have fallen first. This is a bit more difficult for me to get my head around, as the move played was "special" but not something that immediately ends the game.)

Edit: Under 9 schools league game. We decided on the spot that it was a draw without any discussion, but then I started thinking a bit more about it in the evening.