Do I still bear responsibility or sin after losing a sum of money entrusted to me and listing it as expenses, then asking for forgiveness from one of the company's owners and being forgiven?

If money that is not yours is lost, and you were not negligent in its safekeeping nor did you transgress against it, then you are not obligated to guarantee it. However, you must repent to Allah for the sin of lying by recording false expenses. But if you were negligent in its safekeeping, then you must repent and inform the company owners of your negligence and mistake. If they forgive you, then all praise is due to Allah. Otherwise, you are obligated to guarantee it to them. If informing them would cause you harm, then you must return the money by any means you deem appropriate.