It depends on how it's been interrupted, I've heard by top 5 which would of been tonight or top 5.
According to this, once they hit top 5 it goes bye bye
Fast forward to 2013, where "Idol" has just finished its top seven results show. After Janelle Arthur and Burnell Taylor were announced as the bottom two vote-getters, it was Taylor who had to sing to avoid elimination, trying to avoid becoming the fourth straight male contestant voted out. One song later, the save was not used, marking the deepest point into the season in which the option remains.
Once the show hits its top five, the save disappears.
http://www.billboard.com/articles/c...eliminated-as-american-idol-judges-avoid-save