Future Cell probably didn't, but the fact that he was ready to leave that era tells me he was tired of searching for them. This scene is entirely different in the Anime. There, Cell only decided to steal Trunks' time machine and leave for the past after Trunks revealed he took the Androids out.
I'm not sure how the spy robots work, so it's possible it measured Trunks in all aspects. Maybe it calculated how strong he was in Base and Super Saiyan, though it'd make more sense to hone in on the power (Super Saiyan) that he actually used against the Androids. Either that or Trunks' Base exceeded the spy robots highest calculation of his power. In the Anime when Goku transformed to fight #19, they noted how it was different than the Kaio-Ken, which tells me the emphasis was on their Base power and whatever power-up they possessed outside of it.
Future Cell must've thought Trunks was sitting around eating candy during his experiences with Perfect Cell in the past or something. He doesn't even entertain the idea of Trunks improving until the kiai blows him out of West City.