I had received a chest, opened it got the reward but then

I had received a unite licence chest from the event type of thing, which comes when I play after a long time. So from that chest I selected to get the unite licence of garchomp, I received it and then closed the game, after playing the game again after a few days, today I saw that I did not have the garchomp, and the chest was also not in my item box.

What should I do now??