I am with Kevin58 on preferring to be too low rather than too high.
Enzyme activity is still going on, just at a lower pace. Plus you were below the accepted gelatinization temperature of the barley, so I am not sure how your efficiency will come out. I brew some pilsners at pretty low mash temperatures to achieve higher fermentiability.and will give it a longer mash time to compensate for the lower temperature and being on the edge of the barley starch gelatinization temperatures.
Being off that far, I probably would have added a bit of the hot sparge water or pulled a bit of the mash and heated it up to add it back in to bring the mash temperature up to at least above 147 F (64C). While not ideal, it is a quick way to get yourself back in line with intended design.