Ridiculous Blunder

PLAYED  a Scot in this morning's ninth and final round of the Mariánské Lázně 50+ seniors.

White to play and draw in Spanton (1854) - Ian Aird (1857)

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49.Rd4??
The double-question mark is not so much for playing a losing move - the position is not simple - but because I knew how to work out whether the pawn-ending is drawn or lost, but I played the text anyway.
The only drawing move is 49.Re4+!!, and after 49...Kf5, 50.Re1!! Stockfish10 and Komodo10 reckon Black's best try is 50...Rf2 51.Kd4!! Kf4 52.Re4+! Kg3 53.Re3+! Kg4 54.Re1!! f5 55.Ke3! Rg2 56.Rf1! Rg3+ 57.Ke2! So far all of White's moves have been only-moves, and I have tried to punctuate them in line with the John Nunn endgame convention.*
From now on it gets easier for White, for example 57...f4 allows five drawing moves, all with the rook, including 58.Rh1, while 57...Rh3!?, which is probably Black's best shot, allows two, 58.Rg1+ and 58.Rf2 (all analysis courtesy of the Nalimov endgame tablebase).
The game finished:
49...Rxd4+! (still using the Nunn convention) 50.Kxd4 Kf5 (for some reason I had only considered 50...f5??) 51.Ke3 Kg4 52.Ke2 Kg3 53.Ke3 f5 0-1
My final score of +4=2-3 saw me lose 11.2 Fide elo.

*From Wikipedia:
In his 1992 book Secrets Of Rook Endings and other books in the series (Secrets Of Minor-Piece Endings and Secrets Of Pawnless Endings), John Nunn uses … symbols in a more specific way in the context of endgames where the optimal line of play can be determined with certainty:
 ! - The only move which maintains the current evaluation of the position: if the position is theoretically drawn, this is the only move which does not lose; if the position is theoretically won, this is the only move which secures the win. An "!" is used no matter how trivial the move in question; the only exception is if it is the only legal move.

 !! - A particularly difficult-to-find "!" move.

 ? - A move which negatively affects the evaluation of the position: if the position had been drawn before the move, it is now lost; if won before the move, it is now drawn or lost.

 ?? - An obviously bad "?" move.

 !? - A move which makes the opponent's task harder or one's own task easier; for example, in a theoretically lost position, a move which forces the opponent to find several "!" moves in order to win.

 ?! - A move which makes the opponent's task easier or one's own task harder; for example, in a theoretically won position, a move which requires several subsequent "!" moves in order to win (Nunn 1999).

This convention has been used in some later works, such as Fundamental Chess Endings and Secrets Of Pawn Endings by Karsten Müller and Frank Lamprecht, but it can be safely assumed the convention is not being used unless there is a specific note otherwise. The Nunn convention cannot be used to annotate full games because the exact evaluation of a position is generally impractical to compute.