I have seen this posted many places.
Its probably how the game is coded.
Since the event is over, any items in that set likely got deleted if left in when the timer expired.
I'm not sure if this is intentional or not.
The code would need to be modified to have all items in a set returned upon expiration.
I would contact EA live support/email and explain the issue in more detail
https://help.ea.com/en/article/contact-ea-help/
I would also tweet the link to this thread @AskEASupport
Hope this helps!
