Short answer: the Ottomans weren't very involved in the war in the first place, so it wouldn't have made much sense for them to have been a party at Westphalia.

Longer answer: the last big Turkish-Habsburg conflict prior to the Thirty Years' War was the Long Turkish War, which ended in 1606 with the signing of the Treaty of Zsitvatorok. This treaty represented a temporary eastward shift in Ottoman policy, towards dealing with its own domestic problems and confronting the belligerent Savafids. These two goals took up most of the Ottomans' attention, as the Abaza rebellion and two Ottoman-Safavid wars were both concurrent with the larger Thirty Years' War. There was a bit of half-hearted Ottoman involvement in the war, through its support of Gabriel Bethlen and two indecisive campaigns against Poland-Lithuania; and, in fact, the Ottomans were beginning to get more involved in 1639, when they made peace with Persia and could once again focus on the west. But Zsitvatorok was renewed in 1642, and the Ottomans returned to peace with the Emperor; for the remainder of the war, they were more concerned with conquering Crete from the Venetians than anything having to do with the Thirty Years War.

Your specific question is best addressed by the information in Peter H. Wilson's The Thirty Years War: Europe's Tragedy (which is a great book in general on the war and its surrounding period); information on the Ottoman-Persian wars can be found in many books, but I used The Ottoman Empire, 1300-1650: The Structure of Power by Colin Imber.