There are also cases where one should have received miles but never gets them. Many years ago when PanAm went bankrupt and the miles transferred to Delta, I had a 20K miles PanAm certificate which I mailed to Delta. Delta claimed to have never received it, and I had sent the certificate by ordinary mail. I could provide Delta with the certificate number as I still had the other partner ceretificates with me, but Delta refused to provide the miles without the actual certificate or proof of certified delivery. I lost 20K miles then.

So you win some and you lose some. It balances out.