These types of applications usually require a scan in order to detect the items that have been locked. To do this, start the software and use the Recovery or the Scan function to look on the storage devices for the images and videos. However, if that memory card has been formatted when it was inserted in another phone, then it's possible that they're lost for good, and a recovery solution needs to be used. According to the information found on the app's page at Google Play, AppLock has the capability of recovering files. You can do this from the Vault section of the app.
