I ordered OS4.1FE for Classic (intended for WinUAE) from Amigakit.com when it arrived in 2015, and can still see my completed order in account history on their website. However, I forgot to register it on hyperion's website so now I can't access the update. (I did register the former version and got up to update 6 before, but that isn't enough to get the FE update 1).
Since I did pay for it and can prove I have, but have lost the packaging, how do I recover the registration number in order to register on the website and get the update?
It took me a while to locate my copy, but the registration number is on the back of the manual ("boot guide") in the DVD case. If you don't have that, then there's an outside chance AmigaKit keep a record of the serial numbers.
You should keep such details safe for precisely this reason!