It could have been this ending

I reached an interesting position after some horrid play. First, I lost a bishop to save a fraction of a second through premove--an online blitz resource that has cost me many games. As the game went on, I dropped pawns with no concerns for the future. Then, my opponent returned the bishop and let me stop his passed pawn.

We reached this position after many more moves.

Black to move

I played the correct move without understanding my plan.

46...Rf4+ 47.Rf5

White loses with any other move.

47...Rh4?

Throws it away. Later in the game, my opponent missed a checkmate in one, and a checkmate in two on the following move. Then he missed a checkmate in three when time was critical, and five moves later ran out of time to give me a draw.

I could have earned the draw in this endgame.

47...Rxf5 48.Kxf5

Black to move

Both 48...f6 and 48...h4 draw.

a) 48...h4 49.Kg4

Black to move

49...f5+! 50.exf5 h3 51.Kxh3 Kg5 results in a position that is an elementary draw.

b) 48...f6 49.f4

Black to move

49...Kh7 draws if you are a computer.

Simpler for carbon life forms is 49...Kg7 50.e5 fxe5 51.fxe5 h4