What is the ruling concerning the money the questioner took by cashing a check in the name of a subcontractor, and what is the amount that must be returned?

The check is a right for the worker unless the company demands its return. If the company does not demand it, then the amount is his right, and you must return what you took from him. However, if the check is a right for the company, then you must refer back to the company to inquire about the worker's entitlement to the amount, and then pay the amount to the rightful recipient.