Employer didn't withhold federal, social security or Medicare taxes, but did withhold state taxes

Was the income not reported on a W-2?  How was the $7,000 reported on the 1040 income tax return?

In TurboTax Online, wages not reported on a W-2 may be reported as follows:

• Select Federal from the left side menu.
• Select Wages & Income from the left side of the menu.
• Click the down arrow to the right of Less Common Income.
• Click to the right of Miscellaneous income….
• Click to the right of Other income not already reported on a Form W-2.
• At the screen Other Wages Received, select Yes. 
• Continue through to the screen Any Other Earned Income.  Select Yes.  Select Continue.
• At the screen Enter Source of Other Earned Income, select Other.
• At the screen Any Other Earned Income, enter the description and amount.

The entry will be reported on line 1h of the Federal 1040 tax return.

Was your employer perhaps a school or university where you are enrolled?  In that case, they and you are exempt from social security and medicare withholding.  

Box 1 of your W-2 can't be blank, that is your gross wages.  Boxes 2-6 can sometimes be blank depending on the situation.  If you have state wages in box 16 and state tax withheld in box 17, that box 16 number should probably be in box 1 as well.  You need to talk to your employer.