A stable internet connection is required to play Evoker.
If you received an item (Card Piece, Potion, Gems, Gold, Token) from a quest and it does not show up, there was a synchronisation error during gameplay.
When this happens, the game shows you that you received something but could not add it to the database.
This is followed by a disconnect and a forced restart of the game.
This means that the game never registered that you received these items, and that's why they have disappeared. The resources that you used for the action are automatically returned to you.
Evoker is best played on WiFi or at least on 3G/4G networks.
A slower internet connection can lead to several forced resets. Please note that even WiFi connections can lead to slow connections and do not guarantee a perfect playing experience at all times.