And despite facing a partisan 50,000 strong-crowd at a packed Aviva Stadium, Toulouse came mighty close to taking their Heineken Cup defence all the way to Cardiff.
In a pulsating clash that swung one way then the other, Toulouse led in the early stages of both halves before tries from Jamie Heaslip and Brian O'Driscoll and the metronomic boot of Jonathan Sexton sealed a home win.
"As always in tight games, it's the team that either makes the least errors or uses their opportunities the best that ends up winning," said Sowerby, who started last season's semi-final triumph over the same opposition.
"That was Leinster and they were really deserving of their victory. Everyone gave a good performance but it just wasn't enough. We tried really hard but the better team won.
"You look at the game that Johnny Sexton had - I don't think he missed a kick. He certainly had enough penalties and didn't miss one. He scored a lot of points which clearly meant that we made too many errors.
"We're disappointed, obviously. We're disappointed that we lost, but we're happy enough with the performance. It's not an easy place to come to and Leinster are really, really good side."
While Toulouse' latest stint as European kings is now destined to end later this month, Sowerby is confident the continent's most successful side are in a strong position to challenge for glory again next term.
Guy Noves' men have only failed to reach the knockout stages on three occasions in 16 seasons, making 13 quarter finals and 10 semis, and Sowerby sees no reason why that should stunning record should end any time soon.
Toulouse have faced some aggressive criticism for losing close to a third of their domestic fixtures this term, but the four-times European champs still head the Top 14 table by four points.
And South African No8 Sowerby, who has also played Heineken Cup rugby for Stade Francais, believes Toulouse remain in a healthy state.
"I don't think anything's missing and I don't think we've really stuttered," was Sowerby's response to somewhat surprisingly being asked what's gone wrong.
"The Top 14 has become a really tough competition. The old Top 14 sides are used to dominating but teams like Toulon have come up, Racing Metro and Bayonne, there's a lot of clubs investing and it's a really, really tough tournament.
"The level's been raised and it's harder now to got into the top four and the top two. And the Heineken Cup's always been really competitive.
"When it comes to the play-off games in this tournament, there really is such small margins between the top sides. As you saw again today, there was very little difference between us."