Hi Geo,
I had a similar experience earlier this year, when a package i sent was claimed to have been not received by the buyer. The delivery confirmation said it was though, and I went ahead and filed the claim with upic.
Because the buyer had to sign an affidavit that they did not receive the package, i was able to get reimbursed (pretty quickly too), and then reimbursed the buyer for their purchase price. I was kinda mad because I didn't know for certain if the package really was mis-delivered, and the buyer was trying to get a "two-fer". But the buyer was happy, and I guess that's really all I could hope for. At least I wasn't out the merchandise AND the purchase price that I refunded to the buyer. I seriously doubt that if I had used the post office's insurance that they would've paid me a dime lol! That would've been admitting guilt on their part. Anything I ship now that has a value of over $100 I pay the extra for the signature confirmation, in addition to insurance, just to C.M.A.! Hope it works out for you!