If you set the warp in Jabu's entrance, you warp to Jabu with a black screen (Which you get rid of with nuts). All the doors are unlocked, so you can waltz right into the boomerang room, ignoring Ruto completly. There looks like there are 8 stingrays, but only 2 of them actually do anything, and once you kill these 2, the chest appears, facing the wrong direction. WHATEVER you do, don't open it, or you'll just get the map. Just set up a warp, die, save, and warp back to get the boomerang.
Jabu's belly is messed up in general. Enemies appear in wrong places or are missing, all the tentacles are blue, and in the room where you raise the water, the water reaches the ceiling and there is no switch.