The Pole had led the event during the early stages but backed off when heavy fog hit the Portuguese stages.
Kubica had slipped to sixth place when he suffered a double roll in his Citroen DS3. The incident dropped him to ninth, but he recovered to finish sixth in the round of the European Rally Championship.
Kubica also confirmed that he has been using Mercedes's Formula 1 simulator at the team's base in Brackley.
"I can say yes, I was there," he told Autosport. "But I cannot say how many times or how many laps I did. But there is this rumour to which I say, yes, I was in the Mercedes F1 simulator in the past."
Kubica raced for BMW and Renault between 2006 and 2010 but has not appeared in the sport since suffering serious injuries during a rally in February 2011.