They had a warrant for the raid. Or at least they showed me a piece of paper, but my mind was so thrown that I literally couldn't read it (I've never experienced such a thing before or since - I literally couldn't make out letters on the page, such was my state of shock at the time).

I wasn't arrested or charged, they found nothing of what they were looking for on the multi terabytes of disks they seized. No further action other than the raid.

The latter wouldn't be unheard of: https://en.wikipedia.org/wiki/Civil_forfeiture_in_the_United...