Since custo diagnostic 5.x all device starts and reads are logged.
To get information about when a device was started or data was downloaded from this device you can use a page with 5 filter sets in the custo service center.
The page can be found in the service center below (1) "administration" (2) "show device starts".
You can combine the filters (3) to your own search criteria. Than click "Search" (4).
The results will be displayed in area (5).