This tip thing was troubling me so searched the web and found an article on how employers pay employees and tipping. This restaurant may be using the tip credit and the employee was not made aware. Sorry to make you click... I don't think cut and paste from another site is legal.
If the employee is paid less than minimum wage the employer can use the tips to bring the employee up to minimum wage. The minimum wage law is mandatory even for waiters.
http://www.nolo.com/legal-encycloped...employees.html