Lost Card
Are you unable to find a Card where it was originally created?
There are two possible scenarios:
Card deleted
It is possible the Card was deleted, by yourself or a colleague, on purpose or by accident. In this case you can look for the Card in the Trash, which you can find at the bottom of the folder structure on the left.
Card moved
Maybe the Card was moved and is no longer in the place it was originally created.
You can easily search for the Card by typing some of the words on the card into the search bar at the top of the page. In this search you can filter the results by annotations, users, Card type, creator and so on.