[Bobboloo]

That's just bad luck. You must have run over something that bounced up and hit the case.

The engine probably stalled when crankcase ventilation was interrupted which is a good thing otherwise you would have destroyed all the internal parts if you had dumped oil and kept driving.

As long as you didn't drive without oil you'll be able to save the engine.

This area where the case broke can probably be welded. At any rate the motor should be pulled and the oil return tube removed. It's possible you can have this fixed without breaking down the motor.

After welding is complete you can replace the oil return tube with a collapsible one.

Before welding you should get a small grinding tip and lay a valley for the weld bead.

The repair will either work or it will leak oil but it's worth a try in my opinion.

If it doesn't work and leaks oil then look for another case and monitor your oil level closely until you find a replacement.