HumblePint1

My wife and I bought a copy of Affinity Designer some months ago, and liked it so much we upgraded her design hardware to better leverage its features. We are now unable to find the original email with her product key. How can we recover it? I'm also not 100% certain *which* of our email accounts was used to purchase the software. I *am* 100% certain we did not purchase Affinity Designer through the Microsoft Online Store, however (I checked there before posting here). Help?