For Find My to register the location of a device, the device must be turned on and connected to the internet...the system does not maintain records of where every device is for later call-up by users.
Apple does not assist in locating devices without a court order for legal reasons.
If the device has been off-line for weeks, there is nothing anyone can do to help locate it.
To a regular user is very hard to buy that "...the system does not maintain records of where every device is for later call-up by users...", imagine for an app architect such as myself! Action logging is something really basic implemented on any app wordwide, I bet that is not different in the find my iPhone application!
I do not understand what is the problem that prevents Apple from helping locating a device that it knows it is owned by a person (just look at the serial number and associated apple id). I guess it is greedy to lead the mobile devices marketing (and this is NOT the way to go Apple) - there is not other reason why the last known location of a device is not available for the device owner.
As an Apple fun I can tell that I am really frustrated with this situation. I am start considering moving out of this brand because of lack of good will for helping customers solving issues as simple as this one!
If the iPad was running iOS 7, the thief/finder will not ever be able to use it.
iCloud: Find My iPhone Activation Lock in iOS 7
Apple (and no one else) can not assist (with serial number or iCloud) in finding a lost or stolen iPad.
Report to police along with serial number. Change all your passwords.
These links may be helpful.
How to Track and Report Stolen iPad
Reporting a lost or stolen Apple product
What to do if your iOS device is lost or stolen
iCloud: Locate your device on a map
iCloud: Lost Mode - Lock and Trace
iCloud: Remotely Erase your device
Report Stolen iPad Tips and iPad Theft Prevention
General steps to follow for a Stolen iPad
How to recover a lost or stolen iPad
How to Find a Stolen iPad
What NOT to do if your iPhone or iPad is lost or stolen
Apple Product Lost or Stolen
Oops! iForgot My New iPad On the Plane; Now What?
If you don't know your lost/stolen iPad's serial number, use the instructions below. The S/N is also on the iPad's box.
How to Find Your iPad Serial Number
iOS: How to find the serial number, IMEI, MEID, CDN, and ICCID number
Check the serial number (located on back/bottom) in this lost/stolen iPad database. However, most owners are not aware of this database and don’t enter the serial number.
Stolen iPad Database
Also do a search, using the serial number, on your local Craig’s List. Some users list the serial number of a stolen iPad to thwart the sale of a stolen device.
Although it may not be your belief but Privacy concerns are not a "Simple problem"
Apple has done a good job of supplying a tool for use by end users just for this type of circumstance but your device being offline is not their problem.
Good luck with your new vendor of devices as they all have similar diparity and concerns around end user privacy.
Do you consider a "good job" not logging (or informing) in the tool itself the ios device's last kwnon location? What is the Privacy concern with that? How does it differ from providing the current known location? No, I do not see a problem providing that info and yes, I see it tied to the "selling policy" instead.