Steps to reproduce the bug:
Place ONE object in a auto-return area.
Teleport to another sim.
Wait
Watch as you get the notification for your object being returned.
Delete everything in your Lost and Found folder.
Wait.
Watch as you get ANOTHER notification for your object being returned.
Observed results:
The one object gets returned twice.
Expected results:
The one object should only be returned once and should appear in your lost and found folder and shouldn't be returned twice.
Also sent as bug report in SL.