Rode with Menchov for much of the climb? He stayed with him for a few minutes when Menchov was in difficulty after the early attacks, then finished the stage 9 minutes behind him. And with the group having been reduced to that small number, Froome was a hanger-on from the break. He was detached from the group shortly after Johan freaking van Summeren.
It was a pretty good day that indicated one day he could be a decent rider, but nothing that suggested "this guy will win a GT". Augustyn - who is younger - attacking and cresting Bonette first drew more attention and deservedly so. Rigoberto Urán in the final week of the 2009 Tour was far more visible.
There's a reason that the Froome apologists always point to that day as the sign that Froome had the GC talent, and it's the same reason the cynics point to the Taaramäe on San Luca: there's practically nothing else to point to. He did next to nothing noteworthy - either good OR bad - until August 2011.
A few weeks after that Alpe show, Robert Gesink, who's a year younger than Froome, finished 6th on Anglirú en route to a Vuelta top 10. After a season where he'd been 4th in Paris-Nice, 12th in País Vasco, 4th in Flèche Wallonne, 4th in the Dauphiné. THAT is showing the potential that says you can be a GT winner. Being in the break of the day and eventually finishing 30th on the stage is a pretty impressive showing for a young competitor like Froome was in 2008, but if that's all it takes to justify somebody carving the field up like he suddenly started doing in August 2011 with no warning whatsoever and after two years of achieving absolutely bupkis, guys like Christophe Riblon and Amaël Moinard would be GT winners by now.