Money orders are readily accepted and converted to cash, and are often used by people without access to a standard checking account. Money orders are an acceptable form of payment for small debts, both personal and business, and can be purchased for a small service fee from most institutions.
What do YOU think
(a clue - that has you sending a money order and not getting the goods got to do with the post office?
second clue - your contract with the post office was to take the money order and deliver it to the person you sent it to - They did that so they fulfilled their part of the contract.
Not if the seller cashed it.
Will post office refund the money order I sent to pay for an item and the item was never shipped?