Actually, selecting at random from already sifted list of good moves is probably not such a bad strategy. Especially in series of games against the same opponent. It brings in a factor of unpredictability, which may well appear as "superior intelligence".

Doesn't really sound like a bug.

I am so curious about reading the logs, if there was any, during this game. It seems so weird that the default move is "purely random" in case of undecision... I can't trust these declarations...