Few things spring to mind. The mention of carby ice is possible if there was enough moisture around.
Interesting point about on descent, The common training at flying schools is to go full rich on descent, and pulling the throttle back. To lessen the impact of icing during the descent, leave the mixture as lean as possible.
For those who have instrumented their carbs and experimented with this you will know what I mean. It is a significant contributor.
The little O-TCM's are great ice machines.
