Defroster Vent dropped a necklace?

Hmm, I am sorry to hear that, this problems happens and there is no correct answer to help this but I would remove the defroster grill to see if it is there and has not dropped further down, if so, the HVAC system will need to be disassembled to do exploration until the necklace is found. Here is what you are in for when doing the job. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.