I would complete the mash and see what kind of pre-boil gravity you get. There is some hysteresis associated with the amylase reactions before they are killed off, so you have some 'fudge time' at higher temps before you kill them dead. My guess is you'll get some conversion, but less than optimal. Depending on the ph of your mash you may get some tannins, or not if your ph was low enough.
In any case, I don't see why you wouldn't just finish it out at this point...you might be pleasantly surprised.