It was in atti mode (no GPS and that can be confusing and disorientating for inexperienced flyers.
In atti mode the Phantom will hold altitude but it has no ability to hold position.
It's like driving on ice with no brakes.
I suspect that it may have been possible to have flown it back manually if you had more experience.
When it lost signal, it was still moving and would have continued in that direction until it picked up another satellite.
WIth 6 sats, it would have recorded that location as home and found it's ability to hold position and hovered in place until the battery got low which would have triggered an autoland situation.
Here's a screenshot with a yellow line in the direction of drift.
Unfortunately we don't know for sure how far it may have drifted/flown before getting GPS or if the wind may have shifted a little which might move it off the line.
The houses around the end of Rochester Cr might be a good place to search but it could have gone further.