No, what they mean is that someone may have been downloading *advertiser censored* and the CP was in some of it. If something comes from a public source there is no telling what is actually in the file you are downloading. You might think you are downloading a video of the church choir but in actual fact it could be something else. Files from the public areas of the internet are often misnamed and/or have misleading descriptions of their contents, especially with *advertiser censored*. So when they talk about inadvertent downloading, they mean that someone possibly downloaded what they thought was regular *advertiser censored*, saw what it was, then deleted it. The deleted file would still be on the hard drive until overwritten by some other file however, it just wouldn't have its pointers.
It would be tricky to figure that out forensically though, unless there was just so much that it couldn't reasonably have been unintentional. If the CP was a small percentage of the total it was probably unintentional, since if anyone is downloading 100k+ images of *advertiser censored* from public areas of the internet it is unlikely that they could avoid accidently downloading CP as well.
This has happened to us before! We often download British UK shows (like Eastenders) from bittorrent. A couple of times the file was labeled, given reviews (false), and we ended up with some pretty nasty stuff. And the site we use isn't illegal - it's a share file, and you seed it back for others to use.
But now we only seed from users that we know, and not strangers! Lesson learned the hard way
But in SA's case, he has way tooooooooo many files for me to even consider it an accidental download - IYKWIM.
MOO
Mel