The 19-year-old got to see some of the match on television, but had to resume his studies as his 'mocks' were just around the corner.
The youngster is the first to admit he can't believe what has happened since this time last year, with the versatile back taking the chance Eric Elwood gave him during the summer.
He has now become a regular in the side, featuring in all 17 competitive fixtures this season, having started in 14 since the first three games when he came off the bench.
And now he is one of the dangermen Harlequins will be watching out for in The Stoop tomorrow. Henshaw admits he almost has to pinch himself to realise how quickly things have happened for him.
"It was the furthest thing from my mind this time last year. The Leaving Cert was coming up and from a rugby perspective all the attention was on trying to help Marist win the Connacht schools title," he says.
Henshaw, playing in the centre, was the key player as Marist lifted the cup for the first time in 35 years and he was quite content to believe that would be the highlight of 2012.
He was in the Connacht academy and when Elwood threw him in during a pre-season game away to Exeter, the coach saw enough to start him the next challenge match with Harlequins.
"It's good to have played at The Stoop before, although it will be entirely different this time around, but I'm really enjoying it. It is just such a massive step-up from where I was last year but thankfully it has worked out."
Most of his classmates from last year are in college or doing repeats at this stage, but Henshaw is also doing an Arts degree at NUIG and that helps keep his feet on the ground.
But, unlike this weekend last year, rugby will take priority this time and the studies will have to wait until he has done his duty for Connacht in the Heineken Cup.