Delivery Mix-Up

[1HotBoss70]

Had a few items delivered to a few buyers the other day (no watches)...I heard back from one of the buyers and he states he did not receive the correct part...it was the wrong item...stating the item that was in the box was the item stamped on the package of the box ( I did use a box from a different item that I happened to send out to another buyer as that box was better suited for that particular product)...so I contacted the other buyer and asked if he received the wrong product (which would have been a more expensive product of quite a bit of value), and he denies stating he received what was ordered...I then contacted the other two buyers I shipped two that day that had products delivered but were totally different types of products just to make sure no screw ups were made and they both stated that they received the correct products...so either the first buyer is trying to screw me over or truly didn't receive the correct product and it was my fault, or the second buyer knows of the mistake and the value of the mis-shipped product and he is trying to screw me over....how do i deal with this situation?

Thanks