Earlier quoted context omitted.
How were they cheating? Moving pieces when you were not looking? Adding more time to their clock?
What I have seen are: - Illegal moves, particularly with knights. - Adjusting pieces onto squares they are not on: edging a rook towards another square slowly, then "adjusting" it onto that square to essentially get a free move. - Dropping pieces and putting them on new squares. - Double capturing: picking up your piece as though they are going to take it with theirs, then moving one of their pieces to take a differe…
(1) He moves a piece, accidentally another piece tumbles down on the board, he adjusts it, and meanwhile, one of the opponent's crucial pawns magically disappear.
(2) Same as above, with opponent's pawn (or his pawn) magically moving to a better location for him.