Your (product/parcel) was (repaired/sent) on (date) and was shipped via (Courier, Air Mail, Etc) on (date). We can only assume that the (product/parcel) was lost in transit.
Upon receipt of your letter, we reported the loss immediately to the (freight company) and they are attempting to locate the (product/parcel). We should have a report back within ___ days.
If (freight company) is successful in locating your (product/parcel) then it will be forwarded to you promptly.
If, after ___ days, they have been unsuccessful, we will forward a check to you for the value of the (product/parcel).
We are sorry for the inconvenience this has caused you.