Yes, you're getting double taxed for the sale because you are using the wrong basis.  Brokers only have to report your out of pocket cost for this sale.  Since your out of pocket cost is $0 you're double reporting the income: once as compensation and then again as "gain".

Enter the 1099-B exactly as it reads and then click the blue "I'll enter additional info on my own" button.  On the next page enter the correct basis in the "Corrected cost basis" box.  The correct basis is: (# of shares sold) x (per share basis for that lot.)  Your per share basis for any particular lot of stock is the same as the per share fair market value used by your employer to calculate the compensation created by that lot vesting.

Tom Young

(SINCE THE DEVELOPERS CHANGE THE SECURITY SALE INTERVIEW EVERY SINGLE YEAR I'LL NOTE THAT THIS ANSWER'S DIRECTIONS ON HOW TO CORRECT THE BASIS FOR THE SALE PERTAINS TO THE 2016 INCOME TAX YEAR.  I'M SURE THAT THE INTERVIEW WILL CHANGE IN THE YEARS AFTER THAT.)

How can I tell if taxes from a restricted stock sale (RSU) has been included in my income already?  If I am showing a loss on both the short and long term sale, do I need to include this in my return?

RSUs are reported on your W-2. Any withholding would have been included in box 2 of your W-2.

If you had sales of the restricted stock, you should have received a 1099-B. You will need to report these sales on your return regardless if they had a loss. 

The link below has helpful information on reporting Restricted Stock Units.

How to Report RSUs