Don't send cash through USPS!
Yeah, I know, stupid....who would ever do that, well my mother does. She has done it for years for birthdays and Christmas and I guess just got lucky none of the cards with cash never got "Lost". Well luck ran out this year, her 2 one hundred bills to us for Christmas never showed up this year.
I contacted USPS about the loss, they logged a claim for the loss and actually told me its quite common these days as the mail system uses various other carriers to handle the mail along the route to the destination. They mentioned that they have some sort of technology to determine that there is cash inside the card and envelope.
I have to contact another division of their theft department but they are shut down due to the government shutdown for now.