Did the installer throw the box away, unaware all the things still inside it?

Otherwise, he willfully threw property away that was not his. Unless it ended up in his pockets and is now on Amazon for $60. Look for a listing for a Marantz mic as well?

While figuring out the Marantz setup issue, I would be keeping a close eye on this installer. To figure out if he was just careless, stupid, or a thief. None of those selections are acceptable but the punishment gets increasingly severe from just a write up to an instant termination.