A brother went missing. After a few weeks his body was found in a mortuary.

Answer

Most certainly it was not proper. If it was possible to open the sealed bag, then it was incumbent to pour water over the mayyit even if touching him was not feasible. Water had to be poured from head to feet on the entire body.

If opening the bag was not possible, then Tayammum had to be effected. Tayammum is effected with two movements. With one movement of the hands the face has to be rubbed. With the second movement, the two hands as far as the arms have to be rubbed. If the bag could not be opened, then these movements should have been effected on top of the bag on the face and on the sides where the arms are.