The Birr man bought into the mini tour to continue his preparations for the main season and came close to notching his second win since he turned professional in January.
A final round 69 left him just three-strokes outside a play-off for the title on nine-under par - and regretting a few missed putts down the stretch.
Grant said: "I played with the winner, Brandon Knaub, and we were both nine-under on 16 but I three-putted for a bogey and he birdied.
"On the next par-five we both had birdie putts from six feet but he holed and I missed. Then we both birdied the last."
Knaub beat Jack Lander at the first extra hole to earn $10,000 with Grant picking up $2,928.
Waterville's Mark Murphy was 13th on six-under after a third successive 70.
Former Shamrock Rovers winger Grant will be back in Europe next week to prepare for the PGA Europro Qualifying School.
The Offaly man flies back to Ireland next Thursday before teeing it up at The Players Club in Bristol from April 9-10.