If you do not have your W-2 in hand, TurboTax will not be able to download it into your tax return for you. You need to have certain information from the actual W-2 in order to download it to your return.
There is not a tool within TurboTax to allow you to search for W-2s to find one that you are missing.
Take a look at the following TurboTax article to learn more about your options:
What To Do If You Haven't Received a W-2