Bug 30648 made Koha retain deleted_biblionumber in reserves and old_reserves, but did not make Koha use that deleted_biblionumber to display a title in holds history. To recreate: - place a hold - cancel the hold - look in patron hold history, see the title - delete the biblio - reload patron hold history, see "No bibliographic record" - use a report to look at your hold in old_reserves, confirm your deleted biblionumber is in the table