Lower mash temps will break down the starches more slowly and into smaller chains of sugar which are more fermentable. An extended mash time will help it be converted. You're likely not going to get a big mouthfill to this beer but you can make a good beer still.
I wouldn't sweat it to much. My first all grain was a highly acclaimed Sierra Nevada Pale Ale clone from a respected home brew store. I missed mash temp by 7-8 degrees. It was a basic two row with a 60 and 5 minute additions of hops. Turned out very nice but nothing like SNPA.
I went to a microbrewery over Christmas and had a glass of beer. I asked my wife to give it a try. She told me, "I've tasted this before, you made it!"
Of course I didn't make the beer we were tasting, it came from an award winning brewery in Las Vegas. Still, even my wife could recognize the same beer.
All I'm saying is, just because you didn't do it according to the recipe, it doesn't mean this beer will not turn out fantastic!
Edit: Oh by the way, never been able to duplicate the beer. I took no notes, was totally lost in most of the process. Have been trying to match it since with little luck.
