ID Card #89 is a collectible item in Dead Island. It is part of the My collectibles, let me show you them! challenge, and the Gotta find'em all and Nearly there achievements. It can be found in the Prison map of Act IV.
Just before leaving the sewers, during the Devil's Labyrinth quest, go to the left. The card is on the ground next to the corpse of a dead guard.
Can be seen on the following map:
Ignore the exit on the right hand side.