notes app deleted things when syncing to icloud

On my son’s iPhone 15 Pro Max with an Apple one subscription. He had some notes on his phone and yesterday he enabled sync with iCloud notes.

Unfortunately, when he synced the existing notes on his iPhone disappeared, and the ones from the iCloud took its place Does anyone have a solution? We’ve done everything? They are not in the deleted notes.

His backup happened this morning, unfortunately and this sinking occurred yesterday so it doesn’t appear a back up is an option.