The Dutchman, left without a drive at the start of 2013 despite winning last year's Formula Renault 3.5 title, claimed victory and a podium for new squad Hilmer in what was only his second weekend in the series.
That lifted Frijns, who originally agreed a one-race deal with the team for Bahrain, to fourth in the points classification.
Despite such success the 21-year-old Sauber Formula 1 reserve driver admits his future is still far from settled, and that his participation in the GP2's forthcoming round in Monaco remains in question.
"If not for [team owner] Franz Hilmer, I wouldn't be here [at Barcelona]," Frijns told AUTOSPORT.
"I need to find some money, for sure, but I have to wait and see what happens. I did the best result I could - first and second isn't bad at all.
"I didn't get a sponsor from winning [FR3.5], but we're doing our best to be in Monaco. Hopefully we'll get there."
Frijns admitted he had not anticipated finishing first and second after posting a best result of 21st in Bahrain, but said it was proof of how he and the team were gelling.
"I was a bit surprised [by the results]," he admitted, "but we know Barcelona well and we didn't Bahrain.
"[The team just has] good people – great engineers and mechanics.
"I feel at home there, and I'm quick. Driving is my passion; I have to enjoy it, and I am now."
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