So I had finally completed my PVP Revenge Rewards Task and I went to collect it and it reset on me! I checked my mailbox history and nothing showed as having been collected… Kinda upset since I finally had done enough battles for the reward. ):
Hi DarkWolfe! Sorry this happened 
Do you know the exact time this occurred, or as close to it as possible - when you daily task reset? By reset do you mean it completed itself or it disappeared?
You should have received the Task rewards if it was completed, it won’t display in your mail and is rewarded immediately. 
It was roughly 30 mins to an hour before my post… I had just used all my keys before attempting my last Revenge Battle for the key ):
I was at 59/60 before the last battle, then when I went to check it, it had removed all my progress completely with no reward…