Martin Sinner should be ranked. He was playing qualifying of a crap challenger while coaching Abdukhalikov and got lucky.
Yeah, Sinner is ranked 1008, ended up losing to Puerto in that challenger you mentioned, but that was in 2008, he hasn't played in 2009.
Among active old guys Dick Norman is playing some great tennis at 38, just made the French Open doubles final and is still playing some singles. I don't think there are any active players older than that who're doing better.