If you have Accidentally Hidden ALL of your Cards.
you will See an EMPTY my collection Screen, and the Sort Icon is hidden.
If you Have a joker Card, then it will remain an you can still access the Sort / View Icon.
Solution
Go to the Store
type a Period in the Text filter of the Store.
Find a Card that you Own.
Click on it to bring up the Detail view.
then Click on the EYE icon to UnHide this card.
now you can got to my Collection, you will have one Card and the Sort Icon is Visible again.
Use it to View the hidden Group of Cards.
Select All of the Hidden Cards
Click on the EYE icon to UnHide them.
Click on the Sort View Icon and Select the Full Collection Group.
All you Cards are now UnHidden again.