When someone swipes a keycard that is not permitted in the system and has never been added before, the controller will deny access to the building and a "Card/PIN Not Found" event will take place.
Clicking "More Info" will give you more insight into the card details.
You can also use this as a tool for adding cards that do not have a visible token number or if you are unsure of their facility code. Have your user scan the card at the nearest reader to collect the required information and then assign a key with the correct token and facility code to that user.
You may notice frequent "Card/PIN Not Found" events take place right after the same user scans their card. If the user is carrying two keycards in their wallet (ie. one for their apartment and one for the office) the reader will read their valid one and grant access but will also read the other invalid card and log an invalid event.