In my opinion:

Do I offer the buyer a refund of $30,000 and go into debt to raise the money.

Absolutely not. It's not my fault I found more of them.

Do I destroy the chips so the buyers price is protected?

No

Do I just start selling them for $100 each. Of course the original buyer is screwed.

Or do I compromise and save 3 or 4 chips, thus partially protecting the original sell and sell the others VERY slowly.

Hard to say for sure, but I would probably contact the person who bought the chip for $30K and offer to split the profits on the just found batch with him in some way.

Greg