What is the ruling of the Sharia concerning how to restore rights related to theft, fraud at work, and personal use of company property, especially if the owners of these rights are unknown or inaccessible, or if the companies have closed down?

These actions constitute a betrayal of trust and an unlawful appropriation of people's wealth. The amount of money taken unjustly, as well as the money generated from the use of the company phone, must be determined and returned to its owners or their heirs, even if indirectly. If they cannot be found, then the money should be given as charity on their behalf.