☹️ my first guess: did you have a look at your item binder? sometimes rewards and content go directly there without notice (sorting by 'newest' might be helpful). maybe you somehow triggered selecting an item unintentionally?
my second guess: did you try to complete a Solo Challenge afterwards? sometimes completing one more game triggers missing rewards and content. Maybe this holds for the disappeared pack?
if both approaches do not work, you might have to contact EA Help (see contact details below). they should be able to solve this issue for you since they can track your account.
hope that helps. good luck!
EA Help
website: https://help.ea.com/en/contact-us/?product=madden-nfl-21&community=true
twitter: https://twitter.com/EAHelp
facebook: www.facebook.com/eahelphub
