As others have said, filing without having the outstanding W2 is not wise. However, even if you file with Turbo Tax, there is no way to prove that you do or don't have the W2 - no copy is required. You only have to know the appropriate numbers that would be on the form if you had it and that they match with what the IRS has. If the IRS does not have a W2 either, they will be interested in hearing from you anyway.
The order of business for you is to attempt to get the W2 from the person who should provide it. If you are successful fine, but if not. you probably should enlist the assistance of a tax consultant or tax attorney.
If you know what numbers should be on the form, say from pay stubs or something, the IRS will be much happier to receive what you know than to have you try to just skip the income. If you cannot get the W2 form from any other source, contact the IRS and tell them the problem. If they cannot tell you what to do, I would enter the form with information as you know it and have someone help you to find out how to handle submitting it to the IRS.
If the amount of income is not large, and all else fails or costs too much, enter the income as miscellaneous income and submit the tax file - that is, if all else fails. If it doesn't match up with the IRS information, you will then get to work it out with them, but at least not to avoid criminal prosecution. Unlike what you are led to believe, the IRS is pretty professional and does not go out of its way to give a person trouble for putting income on the wrong line of their forms as long as you don't attempt to cheat.
