The Carlin driver lined up third, but dropped down the field along with the other drivers to choose wets as the track rapidly dried.
Race winner Richard Verschoor was the highest qualifying driver to start on the slick tyre in eighth, and took the lead on lap six as the others saw their tyres drop off.
Sargeant says he knew very early on that he had made the wrong decision, but that the safety car helped him to keep the soft compound cool until he was able to pit.
The Williams junior then fought back through the pack, finishing where he started for his third podium in as many rounds.
Sargeant said: “I had a hunch that I thought the slicks would be better.
“It’s difficult when you’re starting third, everyone around you is on wets, if you make that call to go to slicks you could ruin the race for you and the whole team.
“So we stuck with it, it obviously didn’t go my way. I did get mad when I was pretty much last but just phenomenal stop from the crew and then coming through like a train for the first half of my stint.
“On the formation lap I knew it was pretty much a given that we were going to be in reverse.
“I was optimistic that maybe we could hold on until the pit window. The safety car helped us, we could keep the tyres cool.
“Obviously the outcome is good considering the strategy call we made.”
Verschoor, who gambled on the slicks from the start, says he was “quite in doubt” about choosing the slick tyres, and said the early stages of the race were “quite tricky.”
But he too realised early on that the track was dry enough for slicks and that his risk had paid off.
He said: “I saw on the reconnaissance lap that it was drying and only two or three corners where actually we’d lose time on the slicks, so that was the decision for me.
“For me we were quite lucky with the safety car, because the track was drying.
“Mainly Turn 1 and Turn 3 was a bit tricky, braking at Turn 4, but from there on was just about getting temperature in the tyres and pushing.”
