The next day the mystery was solved. About two feet to the left another icicle quickly approaching 3 feet was spotted where there had been none before. This one was hanging appropriately from the corner of the roof. That made me remember that a few days prior we'd had some very high winds. So, i presume that the winds broke off the aforementioned icicle and blew it horizontally two feet in the time it took to fall into the snow below. Pretty impressive winds, in my opinion.
