"Activation Lock is requesting your password..." on a device that was stolen over a year ago.

Keep checking Find My. Your iPad may have been reset and even though it will be of no use to the person who may have it, there was apparently an internet connection made that tried to verify the status and Find My may update its location. Do not reply to any emails or messages that may try to get you to provide your credentials.

Perhaps not. The email might suggest that your iPad has been found and reset - and is now prompting for your account credentials before it can be reused.