Accept the reality of the loss.
The first task of grieving is to accept that the item is gone and will not return. For some, it is a difficult thing which is totally understandable. They hope for a reunion with the lost particularly in the days and weeks following the loss. They deny the irreversibility of the loss and live with hope.
Accepting the reality of the loss takes time as it involves both intellectual and emotional acceptance. Intellectual acceptance often sets in much earlier than emotional acceptance because it takes the mind a longer time to process and accept life without the lost person or item.