There are not many inconveniences that are more upsetting than losing something that has a lot of sentimental value. Some possessions feel like they should be with you for life, and opening up to the possibility that this might not be the case can be an unpleasant shock. They are the kind of things that some will happily do anything to get them back.
The unfortunate reality that many people in these situations have to face is not just that they may never see this precious belonging again, but that the price they have to pay to have it returned to them is far greater than seems fair. Not everybody is going to be fortunate enough to find the thing themselves when they retrace their steps. All kinds of suspicious happenings can take place with a lost possession, not least if it happens to be somewhat valuable. You never know who might be the first person to come across it, and what they will think is the best way to proceed with it. Of course, there is every chance that they will decide that they want it for themselves.