This is completely anecdotal evidence but I pitched 4 packs of notty into a 10 gallon batch once.
The beer ended up at 1.001. Needless to say, I had no attenuation problems. It's possible you did though, but I doubt it.
Seriously - let it sit at a warmer temp for a few days, and see if the gravity changes. The mash temp is good advice, but it won't help you with this batch.
In Process - Russian Imperial Stout, Nelson Sauvin Rye IPA, Mild No.3
In Kegs - Barley Wine, Apfelwein, Wild BlackBerry Wheat, Coffee Oatmeal Porter
Gone - so many :(