Fuel and items in the drill's internal buffer are properly picked up by bots when they are deconstructed.
I looked at it some more I really don't want to add a bunch of custom code for the omega drill. If you don't want to lose items inside it, you should add omega-drill to the Autodeconstruct blacklist.
The Omega Drill author can fix this by properly handling deconstruction of their compound entities. This would have two parts: First, listen for on_marked_for_deconstruction of any "omega-drill" and mark the corresponding "omega-chest" for deconstruction as well. This way bots will come to pick up the chest. Second, listen to on_robot_pre_mined of any "omega-drill", and if the omega-chest is still there, give the robot some items from the chest instead of the drill. That will force the robot to return with the items, and make another trip back for the drill, and repeat until the chest is empty.
This is how I handle the "ship engines" in Cargo Ships and it works great. There are even extra steps you can do to add the hidden entities to undo-redo stack entries.