Here Kasparov to play. (It's a blitz game.)
He played 26...Nb4. His hand clearly leaves the piece for a split
second, See the vid link below, then notices the Bishop fork 27.Bc5
and instead moves the Knight from b4 to f4. The video link to the game:
Nakamura appears to look over Gary's shoulder and then carried on
as if nothing had happened. Did he get signal from an arbiter that it was
OK as Gary had not yet pressed his clock. Were they playing touch
clock which is what some places do. Do you lot play touch clock at Blitz.
If Gary had played 24...Nb4 and Nakamura replied with 25.Bc5.
You would be wrong in thinking the Rook can slip out of the fork
with 25...Rb8 because 26.Bxb4 Rxb4 27.Rc8+ wins the g7 Bishop.
Just for the sake of completeness, here is the whole game. It ended in a draw.
Nakamura - Kasparov, Blitz game 2016