I don't know for sure, but if I remember correctly, the general consensus was that it's probably counterfeit.
Agreed. It's usually the 18650s that support that type of mAh. There are legit Li-ONs on Ebay though. Try to aim for the 900mAh. You might find that they seem as expensive as some better-rated ones, but that's because the 900mAh are legit.
To avoid the problem you faced, I have always ordered an extra set of batteries with my sabers, and have always had a replacement ready to go, you know, if you ever get another saber in the future.