A communications system is provided which can search for information about a communications device that is not registered in a network by designating time. The search system, which includes a plurality of communications devices, gateways and an entity management server, can execute a search method. The entity management server stores in a storage device the identification information of the communications device sent from the gateways with establishing correspondence with notification time. The entity management server receives from a mobile terminal the identification information of the communications device and designated time. The entity management server searches for the identification information stored in the storage device at the designated time, and identifies the location information of the gateways corresponding to the identification information included in the search request.