Is there a way to retrieve expired boarding passes deleted by accident?

I know it sounds a bit strange, but I was manually transferring some old boarding passes (that I'd like to keep as memories) from my old iPhone to my new one. Once I'd passed them, I deleted the ones on the old phone, but then I realised they were disappearing from my new phone as well. Is there a way to can retrieve them? I had iCloud connected and the option for Wallect activated, but I can't find any backup on the iCloud website.