I did not experience this, and actually was the opposite - I felt fine and happy wth sugar levels off the clock (over 32 mmol/l) and I freqently got the ketones warning.  As a T2D, it seemed that my pancreas was still producing insulin, and that in time the level should drop back of it's own accord.  The worry though is that if the pancreas has gone on strike, then trouble looms, so ignoring such high levels if suddenly occurring is not good policy, and the OP took a reasonable step to help reduce bgl by exercise.  I too suspect this was a rogue reading since the bgl was low.  
I need to add my bgl was high three years or so ago, and I was lucky to discover this forum, and learn about the Low Carb diets, which I now follow.  I am T2D and my GP has just registered me as Normal in my notes, and DVLA has just renewed my licence all thanks to this site.  I no longer see those high figures at all, and I have reduced or stopped most of my medication,