There is no way to look up your W-2 if you didn't get it from your employer. Ask the employer to give you another copy, and make sure they have your correct address.
Some employers and payroll services partner with TurboTax to allow you to import your W-2. But in order to import it you have to enter a code or amount from the W-2. That requirement is for security, to prevent someone else from stealing your W-2 and filing a tax return in your name. So you have to have the actual W-2 from your employer, even if you are going to import it into TurboTax.
