Definitely robbed out. The bigger questions to ask are “why was the hive was so weak in October so it couldn’t defend itself?” And what could you have done better to prevent the event?
At this point, it’s hard to say whether bees absconded or if they was a “queen” event earlier in September. This is why we August inspections and remediations are critical for the hive. This happens (or has happened) to all of us but as we gain experience and understanding of keeping bees you will learn to keep your hives healthy as we go into the fall and winter. It is very likely this hive would have failed over the winter anyway. Take the loss as a lesson. Its ok we all take losses- we all are trying to be better at reducing those losses.
At this point my best advice is regroup for next year -keep reading/learning, take the intermediate class, come to meetings and talk to members so we all can learn.
Its a sad lesson but dont give up!
K