Were you able to boost the temperature? In my opinion, low mash temperatures are better than too high. 143? is not where I would want my mash however and I would find a way to raise it to meet your target. If this is where your mash stayed it is likely you could have poor starch conversion and a watery beer. It's also possible that you had some stratification in your mash with varying bands and pockets of temperature differences. Either one of your readings could not have been completely accurate with your actual mash bed temp being somewhere in between.
Bottom line, stir your mash well at dough in and take temp readings in several places. If you see wild fluctuations, stir some more. If you missed your target mash temp too low, have some boiling water on hand to mix in and raise the temp. If it's too low, use cold water. As the boy scouts say: be prepared.
Let this beer finish out. At worst it will be an experiment on the affects of low mash temperatures. At best it could turn out to be a thoroughly refreshing lawnmower beer that your friends will rave about.
