What you were expecting to happen, and what actually happened?
I had a notification that I had an uncollected reward. Instead of collecting the reward, I visited the Hero tab. Backed out of that screen and found that the guild notification had vanished, with the rewards added correctly to my collection.
What are the steps to make it happen again?
On the iOS version, visit the Hero tab while a guild reward notification is pending.
Can anyone else confirm this behavior?