It's not theft of the digital entity, it's theft of the time and effort that went into creating the digital entity. The relevant concept is Theft Of Services.
Theft of services still implies the consumption of someone else's resources. By not paying for the service, the provider faces tangible losses (because the opportunity to service a paying customer is lost). In this particular case, Apple loses absolutely nothing. The designer is still wrong (and IMO, plagiarizing copyrighted design assets merits termination), but Apple's capacity to service their customers is not hindered by this.
