The date and time for "Last Discovered" under Monitored Devices' Polled Metric Families does not change after a re-discovery. The date and time stays the same.
Why doesn't the "Last Discovered" date and time change after re-discovering the device?
PM 2.6 - PM 3.2
Under Monitored Devices, select the device that you want to rediscover. The device information displays in the "Polled Metric Families" view.
Click the Update Metric Families button.
Click Yes to confirm.
If nothing in the device has changed, the "Last Discovered" time will not change after a re-discovery.
If something in the device changed, then the "Last Discovered" time will update.