Steps to reproduce:

1. Open attached project (link in edit)
2. Build 'TestScene' for iOS
3. Build and run the Xcode project to a device
4. Click anywhere on the plane,
5. Observe debug log where each time you click on a plane, RaycastHit.textureCoord values are returned at the clicking point

Expected behaviour: Vector2 values anywhere between 0 and 1 should be returned
Actual behaviour: Doesn't matter where you click, Vector2.zero is always returned

Doesn't reproduce on Editor/Standalone/Android.

Does not reproduce with 5.1.4f1