Sport mode is full ATTI in DH firmware.
Gps Off.
RTH will not work / get triggered.
Sensors Off.
If you enter that mode mid flight and want to exit again it is advisable to lower the craft to below 100m get the TOF bottom sensors working again.
This mode is used to launch the drone very fast into high altitude upon turning on, nothing more (well theres also benefits in situation of signal jamming but thats not relevant here). It allows you to do this because the altitude limit is not being triggered when there‘s no gps yet and the launch will happen with full manual motor and propeller stress.
Your drone drifted away in the wind until the battery ran out or it crashed into a tree somewhere.
Sorry for your loss