By Mark Lamport-Stokes LA QUINTA, California, Jan 20 (Reuters) - Charles Howell III had bitter-sweet feelings after failing to secure a place at this year's U.S. Masters when he lost out to fellow American Brian Gay in a three-way playoff for the Humana Challenge on Sunday. In pursuit of his first PGA Tour title in six years, Howell narrowly missed a five-foot birdie putt at the last for outright victory in regulation play, then bogeyed the second extra hole to effectively hand Gay the win.