The former Jamaican National Team coach borrowed the new S-Blade Greenstreak from club member John Kelly, who was out of action with a back injury.
And the 40-year-old Pro promptly took just 29 shots on the course's par 36 front nine holes during a friendly game with four other club members.
It's the first time he has ever broken 30 shots for nine holes and he required only 11 putts in the process.
Now the father-of-two, who lives near Bourne, is refusing to give the putter back to John.
Ian said: "It's brilliant. Throughout my career I have always been good from tee to green, but I've never sunk enough birdie putts of any significant length – from 12-15ft and beyond.
"But the ball roll off the S-Blade Greenstreak was exceptional and I hadn't experienced anything like it before.
"The ball just seemed to want to go on and on – and my confidence level over important putts was sky high, and still is."
Ian recorded two eagles and four birdies in his half-round and could even afford the luxury of a bogey on the difficult Par 4 ninth to still break 30.
He would have played the back nine too – but was beaten by bad light.
Ian added: "I have to admit, I got a bit of a ribbing on the first hole when I pulled the Greenstreak from my bag because it is very unconventional in looks.
"But by the time I had sunk my fourth birdie the Mickey-taking had stopped – and by the end of our game all the other golfers wanted a go. John's not getting his putter back – it's phenomenal."
The S-Blade Greenstreak appears to have winning powers. Owner John, 43, used it for the first time and finished second in Rutland County Golf Club's midweek medal in June.
He said: "I can't believe Ian has snaffled my putter. I loaned it to him to try and it looks like I'll never see it again."
But putter manufacturers Spherical Blade, based in Cardiff, have promised to send Ian his own model.
Managing director Ian Smith said: "We're delighted for Ian.
"To play nine holes in just 29 shots is an incredible feat and an S-Blade Greenstreak is on its way. John can sleep easy."