How to prove that I bought an adobe product, installed it, but lost file and serial number..?

Hi all,

Last year, I bought the Adobe Premiere Element 11 (by downloading it, no CD), installed it on my PC and now, had a problem with my ext. backup disk. There is no way to recover the datas, which was confirmed by a lab.

However, the execution file of Adobe Premiere Element 11 was on it (ok, I know, I can downlaod it again), but i lost the registration key with it.

How can I prove that I bought the product in order to get a new licence key or registration code ?

Thank you folks for your suggestions / solutions !