Maybe you follow casey neistats vlog. In one of his latest installments he apparently flew a drone out of a hotel room.
Look at 8:10

I assume gps reception will be weak, home point will be useless. RC conmection will be weakened by building shadowing the waves.
What precautions would you recommend to bring the drone safely back in?

I assume gps reception will be weak, home point will be useless. RC conmection will be weakened by building shadowing the waves.

Most likely flying his Mavic anyway... The building density from the short clip looked pretty open, so GPS and RC connection would be fine?

What precautions would you recommend to bring the drone safely back in?

A long arm and the preferred 'Catching hand'?

According to the manual, flying out of the high from ground window is not recommended.

I enjoy watching a lot of what Casey puts out, but he definitely is not the model of what people should emulate....   He probably just broke about 83 German laws in that 10 second clip!  Also, keep in mind that Casey has a whole collection of broken drones and camera equipment.  So unless you have a very high level of risk tolerance (and bank account) like Casey, I wouldn't recommend doing what he does.  

I also agree with LegacyOne from above, I would guess Casey was using a Mavic Pro, not a Spark which seems to be quite a bit more robust in its RC robustness.  

The description for the video indicated he was using a P4 and not a Mavic. I suspect he used ATTI mode to get in and out of the window and then switched to P mode once outside.

I at least had great fun watching.
Usually do with CN.
Thanks for the video