Upper right corner on page 48.
Are you sure you didn't press RTH.
As long as the 4 LED's on the RC are NOT blinking together, you can still controll the drone (no disconect) and RTH should NOT be initiated automatically.
I think you got cunfused...
Did you read the manual?
A disconnect between the RC and the phone does NOT result in not being able to controll the drone.
In fact: you can fly any DJI drone with the RC alone (no device connected).
A common cause for "RC not connected to mobile device" is accumulated lint/dust inside the USB-C port of your phone.
The data pins on this connector are slightly shorter then the power pins therefore charging your phone still works "Connected for...
It's important to understand the limitations of your equipment.
Your drone's height measurements are all done with a barometric sensor that measures air pressure and all heights are based on the power up location = 0 metres.
Setting heights...