Yes indeed the 'forensically searched' comes from TW.
I was thinking in this situation, if the police came to my door (home or business when I had my own) and explained that they were dealing with a missing person case who was last seen very close by and they'd like to just take a look around my property to check for them, well I'd be fine with that. No problem to let them check outbuildings, have a look in each room, under the beds, in the wardrobes, heck even stick their head up through the loft hatch to have a look in there, I'd be absolutely fine with it.
But I wouldn't be fine with my property being dusted for fingerprints or DNA and if the circumstances were the same as this case, I'd insist on a warrant for that.
To me, "forensically searched" implies just that. Dusted for fingerprints, documents checked, DNA etc. It's that word 'forensic'. It suggests much more than a few police officers having a look around the building for someone who may be there.
This is why I'm wondering how other posters interpret "forensically searched". I don't think those businesses have been searched in the way that I interpret those words.