Kubica, Deletraz and Yi Yifei led onto the final lap in WRT's maiden attempt at the race two years ago, only to be foiled by a freak throttle sensor failure that caused their engine to shut down and meant they were not classified.
After spending 2022 at Prema, finishing second at Le Mans, Kubica and Deletraz returned to WRT for this year's World Endurance Championship and led for a total of 39 laps in the car they shared with Rui Andrade at last weekend's 24 Hours.
Despite a foot injury for Inter Europol Competition's Fabio Scherer, the Polish entered car was out of reach in the final hours and finished 21s clear at the finish.
Vosse, whose WRT outfit will run BMW's World Endurance Championship programme next year, told Autosport that his disappointment at missing out on the victory was heightened by the previous misfortune suffered by Kubica and Deletraz.
"At the end of course I’m disappointed and I was dreaming of giving back to Robert and Louis what we lost in 2021," he said.
"We could not make it, we have to accept it and start from now working for next year.
"You don’t come to Le Mans to finish second. If you have a lineup and a team to win, you go for the win. We did not, we finished second but we are leading the championship."
After narrowly missing out on victory for a third year in succession, Kubica said the Inter Europol Competition effort was "out of anyone’s league".
"We have seen in Spa that they have been very strong in the last part of the race and it has also been the case here in Le Mans," he told Autosport.
"We push, we push, we try to put pressure on them, but to be honest they were out of our reach.
"From one side of course being second I’m disappointed but it’s an important day for Polish motorsport as a Polish team and Polish driver won Le Mans so congratulations to them, they have been better, more clever than the others."
Kubica added that he was "proud" of his Le Mans record because for "three years in a row, we were always there".
He added: "Actually I was leading last year, after the first stints of the race I was leading this year, but it was not enough."
The second WRT entry of Robin Frijns, Ferdinand Habsburg and Sean Gelael finished fifth after a final-hour suspension failure dropped them from third.
But after incurring damage in the rain shower on Saturday when Habsburg clouted the barriers and was hit by Lilou Wadoux's aquaplaning Ferrari, the Austrian was delighted with the team's recovery.
"I never thought not giving up would reap such rewards, ever," he said.
"Sticking with it, believing in the car and the team and going aggressive on the strategy, meant that we were back in a place to finish on the podium, which we couldn’t believe from being last and a lap down. It rarely happens.
"Just in an unlucky coincidence, we got a damper failure at the end which means we finished fifth and not on the podium, which I think would have been awesome.
"It was a really fun race, just without the podium pictures at the end, but I can live with that."
