finding a deleted sheet

You could open the Numbers file and go to File > Revert To > Browse All Versions..

Pick the version before you deleted the sheet.

Restore an earlier version of a spreadsheet in Numbers on Mac - Apple Support

Edit:

Please make first a copy of the current status.

New inputs will be lost when you go back to an older version.

Ralf

Enter Time Machine and work your way back to and open an earlier version of the document. If you know when the sheet was deleted, the most recent version prior to that time would be your best choice.

Regards,

Barry