If I appropriate your lawn mower, you no longer have a lawn mower. That's "stealing". If I use intellectual property that you own without your permission, that's copyright infringement, but you still possess both your property and your rights to it. That's not "stealing".
It is possible to steal IP though. If you assert ownership of an intellectual property, then your next step can be to stop the original artist from claiming royalties. An example would be the companies claiming ownership of public domain films and then getting youtube to yank the public domain versions.
So if NBC was claiming they owned the Apple artwork, its stealing because that ownership (if uncontested) allows them to collect royalties, etc.
