Originally Posted by fzwinter
Even if they've reused the ticket number, you can still retrieve itineraries and print out receipts on ual.com. Just go to "my itineraries" and click on "view past trips." There you will find current and completed itineraries for the past 13 months, with an option to print out a receipt for any of them.
Good luck!
But not all of them show up on united.bomb. Recently, on various occasions, I wanted to print e-receipts for past trips. Three times the e-receipt was not available. Now I try to remember to print them before I fly, because after they aren't always there.