User blog comment:Miskos3/Fairy Tail Episode 189: Gloria, Review/@comment-112.198.82.48-20140705190207/@comment-7418318-20140707095851

If you mean that we don't know whether she lost the hand when Castle Mercurius collapsed with her still inside or she lost it to one of the 10.000 Dragons, then yes we don't actually know.

But my guess would be the former, since I doubt a Dragon would rip her arm off and then spit it out. Also they aren't very likely to let Lucy live.