The same thing happened to me, in last season's CUP Final!
I score a goal before system went down, when It came back up, that goal became an injury for my player

Good news is I still won the CUP during extra time.
I think if you are in a match and server goes down, it automatically generates a result, in which both parties will not be present, and using their algorithms come up with a result. Not sure if anything can be done though, if you did any screen captures before the system went down, and send it to Nordeus Support.