A last known location of a tracking device can be determined by using location information received at a tracking system. A disconnection event is received at the tracking system indicating that a tracking device has disconnected from a mobile device. In response, the tracking system can generate a last known location for the tracking device. Other relevant location updates, such as recent locations of the mobile device or locations of other mobile devices that connect to the tracking device are collected and associated with the disconnection event. Based on the location updates, a last known location of the tracking device can be computed and stored.