I’m an idiot, so I am probably just not understanding something.
But I’ll play the quick battle, and place at a certain tier. I see what rewards are given for my tier. Then the session expires and… nothing.
If I play an event I’ll usually get something in the inbox alerting me to a reward, but nothing from the quick battle.
It’s not a big deal, I mostly play just to get experience points. But I would like to claim some gold or card pack.
Have you checked your inventory? I often receive QB rewards straight into my library - I have to manually check for cards of particular color and rarity to see what I got. Also, QB rankings change all the time. Make sure you finish in the right tier, not just get into it (a silly advice, I know). If you’re sure that you reached a certain reward tier and didn’t receive any rewards, open a ticket with Customer Support.
Same thing has happened with me several times. I even took screenshots and submitted a ticket with them, describing the issue. The response I got was “please describe the issue and include screenshots if possible.” 
I assume quick battles are xp only. I never get non-xp rewards anymore. I just finished 99th and got nothing. If I finish 1k plus I get a notification and my xp, but if I finish sub 1k nada.
I rarely get notification of the prizes I win in quick battles, but they’re there when I check my cards (and it’s always a duplicate).
Seconding this. Really annoying to have to look through my cards to see if I got anything good.
Hey guys, just wanted to let you know that this is a known visual error right now. If you in a match when Quick Battles end and rewards are sent out, you won’t receive the rewards notification you’re used to seeing. Because of this, it might seem that you didn’t receive rewards despite actually receiving them. Rest assured that these items are sent, despite any lack of notifications.
I end quick battle with rating 47, so i should win a booster and rare card. But i check rewards and my cards, i know that sometimes rewards don’t display a notification, and there is no booster and duplicates. QB end 3 hours ago.
Have you tried reloading the game? Sometimes it takes a quick refresh to see the rewards populate.
In addition, have you opened the notification signifying the event has ended? It won’t show the reward notification, but you’ll still need to open the event notification to receive the rewards.
I have noticed that if you shut down the game before the time period ends that the rewards will be there when you log back in. My recommendation is don’t be playing the game when it ends and you’ll be alright.