Scoresheets although provided by the organiser are allowed to be retained by the players. When the organiser wants a copy of the game, the accepted practice is that the top copy is handed in with the result and signatures of both players, leaving the carbons in the hands of the players. Where only single scoresheets are supplied, or none at all in the case of rapidplay, a results slip or similar is used for result reporting.
This is what the FIDE Laws of Chess actually say
They don't on the face of it give the player the right to a copy.8.3 The scoresheets are the property of the organiser of the competition
This is from Tim Spanton's blog
https://beauchess.blogspot.com/2025/02/duff-ed.html
I've seen players use phone cameras to take copies of the opponent's scoresheet in league matches with 10 second increment where the plyaer had stopped scoring with under five minutes remaining.at the conclusion of my game we were informed we could not keep the scoresheets - there were no carbons - as they were the "property of the congress."
Instead, it was suggested we take photos of the scoresheets (presumably with smartphones we should not have on our persons).