If you want it in a pretty-ish form for a particular device with a bare minimal of additional work, find the page for the device in the webUI, collapse the menu, print the device management command history page, and attach it to the disposal report.
For more detailed work, the information is in there, but it'll require a dive into the API and parsing the results into something presentable. Hopefully the following will point you in a useful direction:
If you want the just an acknowledgment of erasures for a batch of devices, pull the info on all uses of the EraseDevice command from the API and parse out what you want.
curl -u ${username}:${password} -X GET "https://yourjss.url:8443/JSSResource/mobiledevicecommands/name/EraseDevice" -H "accept: application/xml" If you want acknowledgement of erasure for a particular device, pull its command history. There are separate timestamps for the command being sent and acknowledged.
curl -u ${username}:${password} -X GET "https://yourjss.url:8443/JSSResource/mobiledevicehistory/id/${device_id}/subset/ManagementCommands" -H "accept: application/xml"${device_id} will be the numeric id of the device object in Jamf. Getting that from the device name will require a separate MDM command.
The above are for the "Classic" API, which will be sunset at some point in favor of the modern complex and modern UAPI, but I don't know of any date for that having been set yet.
