Unfortunately, if you were covered by a retirement plan at work for any part of the tax year, you are considered to have been covered the entire year. Generally, if contributions are made to your 401(k) during the tax year (either by you or your employer), then you are considered covered the entire year.
You can still make a Traditional IRA contribution and may still be eligible for a deduction. When you are covered by a plan at work, then there are income limits used in determining any eligible deduction.
Please refer to the link below for a table defining the income thresholds for the deductibility of a Traditional IRA when you were covered by a retirement plan through work for the tax year.
https://www.irs.gov/Retirement-Plans/2015-IRA-Deduction-Limits-Effect-of-Modified-AGI-on-Deduction-i...
