Report it to chess.com, adjudicating something like this in a forum does nobody any good and it appears like speculation.
FOG- CHEATER
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I had a look at the game. I'd need to look at more of that player's games, but it could be a one-off because he's come up against such a high-rated player.
In the normal course of FOW, opponents "hang" material but you don't know it isn't defended so don't capture it. Similarly they may present winning opportunities that you'd grab in a normal game but don't know actually exists.
There are, of course, times you gamble, form a cannon or a lot of pieces attacking a square and hope you outnumber your opponent or you hit them with a checkmate. It may work or it may not, and against a far higher rated player you go for it.
I AM ABSOLUTELY SURE HE/SHE IS CHEATING. YOU GUYS WATCH AND COMMENT WHAT YOU FEEL.
https://www.chess.com/variants/fog-of-war/game/20635477/76/3