Just tried what @MosesMalone31 suggested and it 100% worked, guy was 3-0 up against me and it never counted as a loss on my record, don't feel too bad about it though because I had someone do it to me in the game before. It's a pretty grim state of affairs for a game that promotes itself as a competitive e-sport haha. To clarify btw what I did to make it happen was to click with my mouse (I play on PC but use controller for FIFA) on my second monitor screen, game did exactly what @MosesMalone31 describes, searched for a bit then gave the "we'll try to determine result message" then I switched back to my controller, hit "a" to confirm, looked at season history and match isn't there.