I being a noob and an official ******* had this happen.
Phantom in office, on floor, idling, showing the wife and I turned the controller off - device took off per design to last "home" location which was 30' outside - through my knee. Scar will be there to remind me:
1- never put props on when device is running in house
2- NEVER turn of RC. Never in house! Only as last chance.