Dropped my necklace down into the vent on the dash, how to get it out?

I was driving off in a rush the other day and left my 18ct gold necklace on the dash. As I was driving and had to stop quick it slid into the vent. I couldn't pull over right away, so I kept driving and after another turn, I heard it slide down into something across the other side of the car. So, this item is very important to me. Also, my husband isn't a mechanic but is very handy in this area. But for the past 3 days he has been working on getting it out. Hes done everything from removing fan and motor, the cabin filter, glove box, and some of the vent line (whatever the heat comes out of when turning it on). We have still not found it and would love some advice! Also, my husband wants to know is it worth taking the heater core out? How much more work am I getting into? Would love any help and advice you have on this subject. Please!