I know its of no help now, but if yo tell the gateline staff at the time when the gate keeps your ticket that you need to to claim a refund, sometimes they are willing to open the gateline machinery and fish the ticket out for you.
I'm confused as to how an East Croydon gate managed to hold onto your ticket. Presumably you went through the gateline, and then realised the trains were cancelled, and exited back through the same gateline. I wouldn't have expected an exit gate to take a ticket valid for travel from the station where the gate is at.