Is it permissible to keep trousers found in a bag, after three days have passed since they were announced and their owner has not returned?

The person who picks up something that does not spoil (such as clothes) is obliged to announce it for a full year, and it is not permissible to dispose of it before that. If a year passes and its owner is not found, the property enters the ownership of the finder, with his guarantee to its owner whenever he comes and claims it. However, if the found item is something minor and insignificant that people of average status would not bother to look for, then it is permissible to own it without announcing it or returning its equivalent.