That is true, but Senna also had to pit to replace a puncture, drove a damaged car from T1 and was ahead of Ricciardo all race, until Massa went kamikaze
How the race actually panned out if you followed Ricciardo:
After pitting he was 20 seconds behind Senna. By lap 13 he was under 7 seconds behind. The real problem Ricciardo had was overtaking which is rather understandable when you've got a damaged car that is pulling to the left. Pic became the next man up the road after Senna cleared him in 2 laps. However Heikki pitted the lap after and came out just behind Dan (Dan had caught Pic by 3 seconds that lap).
So on lap 15/16 you had a three way fight covered by just less than a second. I don't think we saw it, but the end result was Heikki got them both and Ricciardo overtook Pic. On fresh rubber Heikki was able to pull a bit of a gap on Ricciardo and maintain it until the Aussie pitted.
He was then a lap down but had very respectable pace until the safety car. Contrary to your belief, Ricciardo had already overtaken Senna on the first racing lap when the safety car went in. That's 5-6 laps you've managed to completely miss. Then he tried a move on Massa, lost his position, but thankfully then managed to avoid the Massa / Senna collision. Quickly caught up the few seconds to Vergne, them both overtaking di Resta on Lap 50. They followed in very close company and we know how it worked out!
Overall, he was unfortunate at the start with an overly cautious Webber in an ever decreasing space in front of him. Survived that only to be tagged and consequently tagging Senna. Just a racing incident caused by too many drivers taking different approaches on the same bit of track. The safety car did help him, but it also helped a lot of drivers and I don't think it should detract from what was a great drive from Ricciardo.
That's not to say Vergne didn't do well too, he suffered a lot from traffic he could not clear but managed to avoid making any silly moves that we often see with rookies while showing flashes of brilliant speed.