That is because you are not familiar with the game...
Sosulin - Pechenov
Your game was very good by the way and although missing a mate in one,
with a an idle Rook on a1 and a killing check in the position it is entirely
understandable. Not forgivable, but understanable.
(I have missed mate in one twice OTB - I won both games, they cropped up mid
combination - I saw the mates in 3/4 but missed the one movers).
Check all Checks
(we are in good company...Kramnik)