There are several items listed on his W-2 that he will not get back. These are things like social security tax withheld, medicare tax withheld, and local income tax. In some counties there are ways to get the local taxes back if he doesn't live in that county and files to get it back from the local government. That's something I know nothing about.
He would only get refunds, depending on his income from the federal tax paid from the federal 1040 and the state tax back from his state tax form. You didn't mention if he had a summer job, internship, or things of that nature. If he had substantial interest from bank accounts, certificates of deposits, dividends from stocks, those can certainly count as income and prevent him from getting the refund he expected.
