I don't know too much about how the scene works, but from what I understand a dump is when a person or group well, dumps...or rips something I guess, and it is in a form that can be shared.
This does NOT mean it's publicly available. Often it is spread among providers first to make spreading the file to the masses easier.
On top of that, I don't think scene releases are ever uploaded to sites by scene members themselves. It's other people who grab the file and upload it later.
Then there's the whole issue of if the dump is a valid dump according to scene standards.
On the other hand, if it's a dump by some random independent guy, you'll probably find it on some torrent site.
Of course, you risk all sorts of bad things by grabbing dumps like that.
I'm probably wrong on some points, but I don't think I'm TOO far off.
Certainly don't mind a lesson though.