If I steal a snickers bar from a shelf, the store owner has one less snickers bar regardless of whether I might have paid for it were I not able to steal it.
But copying doesn't deprive the owner of their property at all. It simply creates a new copy of it. If I copy an mp3, the record label and artist aren't deprived of anything.
And, thus, the law makes a distinction.
However, the copyright owner is being deprived of their exclusive right to the content. They have the right to control who uses the content and for what (exclusive of fair use).
But no-one's arguing that copying isn't wrong or a civil and possibly even criminal act. I'm explaining the distinction between infringement and theft, as it's far more relevant than the ultimately unknowable "whether or not the unjustly enriched party may have bought a license".
Was the point I was disagreeing with. (Especially as we're being pedantic about the legal issues).
Copying a single song has punishments up to $150,000 with possible federal jailtime at that?!
One hell of a distinction.