Pros: excellent material for a music video mocking the cops doing the search.

Point of order: multiple music videos, not just one.

In other places in the world they can only search room by room so that you can be present and oversee the process.

In America maybe. This was in Sweden.

Yes it was. I don't understand how you could have a functioning legal system anywhere if a search warrant can be neutralized by saying "I don't have that" without any kind of search taking place.

If the search warrant says "take servers containing information about X" and the search team asks which servers contain information about X and gets answer "none" which they have reason to believe it's true - then there's no point taking anything and not taking anything would not hurt the function of the legal system. Of course cops may go on a power trip and take stuff anyway to show how powerful they are, but that has nothing to do with the legal system. Apparently these cops weren't of that sort, congrats to them.