Nonsense. Lots of contracts can last after you stop being an employee, e.g. Non-compete contracts, non-disclosure agreements etc. If the employee leaves the day before their final salary payment is due, does that mean the company is no longer legally obliged to pay them? No.

"Once you leave a company, all your contacts are ended."

Um, no. Assuming you meant "contracts", but in either case, no. That's not how it works.