Losing a game, what was a draw.

I lost the game, when i ran out of time, but my opponent has only 1 bishop. In the chess rules,.thats a draw,.becouse my opponent cant win the game with only one bishop and king.

Assuming you are talking about this game:



It is draw only after fxe5, which hasn't been playes yet, so it is lost

If you want to draw, then you must get rid of your pawn. You lost on time. A series of legal moves exists where your opponent checkmates you with his lone bishop, thanks to your pawn. So according to the FIDE Laws of Chess it is a loss for you.

6.9 Except where one of the Articles: 5.1.a, 5.1.b, 5.2.a, 5.2.b, 5.2.c applies, if a player does
not complete the prescribed number of moves in the allotted time, the game is lost by
the player. However, the game is drawn, if the position is such that the opponent cannot
checkmate the player’s king by any possible series of legal moves.

First of all, there's no fxe5, pawns do not capture backwards. Secondly, even if the capture was possible, black isn't forced to capture. And finally, what tpr mentioned - if you timeout, you lose (with the exception when you can never setup a position with the material left on the board that is a checkmate for the side that timed out). Here checkmate is still possible, for example lichess.org/analysis/6nk/6B1/6K1/8/8/8/8/8_b_-_- So, you lost on time.

@bufferunderrun Yes, sorry, fxe5 is not possible (but in an a chess diagram, white is conventionally located bottom...)
In this case, it is "even more lost"