Missing Item from Envelope

[vhs197318]

I sell coins so many times I mail them by standard envelope.  A buyer recently contacted me stating the coin I mailed was missing from the coin insert inside the envelope and looked like the envelope had been taped. The only conclusion I could come up with was that it had been stolen.  I replied to Buyer and recommended he first contact Ebay because  I am not aware of how this should be handled and that I believe the item is insured up to $20. I have not heard back. Now what should I do? 

[vhs197318]

Mail carriers do get tempted, but not a smart thing to steal. Our technology is too sophisticated to risk a job and benefits for a $50 gift card or something silly like that. But there are petty thefters who can't help themselves and do it anyway.  

[desert_sewer]

This just happened to me and I called Ebay. They told me NOT to refund the money as I needed to open a case and it would be resolved in 3 days. Once before buyer claimed they never received an item yet the tracking showed the postal worker left it at a neighbor's house. They insisted the neighbor did not have it. I told them I would ask Ebay. EBay refunded the money to them, I did not have to reimburse them. I found it frustrating that perhaps they were lying and eBay did not make a further investigation but they said a person can file a missing items case once a year. No questions asked.