In an automated library, data cartridges, such as magnetic tape cartridges, are stored in storage cells or shelves and accessed by data storage drives. An accessor with a gripper transports cartridges between storage cells and storage drives. Cartridges on the library floor may damage the accessor. A cartridge sensor is provided and positioned to detect cartridges on the floor of the library. The sensor may be mounted to the base of the accessor, may be mounted to the gripper, or one or more sensors may be mounted proximate to the floor of the library. If the library includes more than one library frame, a sensor may be mounted proximate to the floor of each of one or more of the frames, thereby allowing for the location of a dropped cartridge to be identified.