Created mutlibody disappears upon simulation

[akhilsathuluri]

I create a new instance of my robot which is loaded using loadURDF. The new instance is created using createMultiBody. Upon stepSimulation, the newly created multibody disappears and the query for it using findBasePositionAndOrientation returns ((nan, nan, nan), (nan, nan, nan, nan)). However the initially loaded original model behaves as expected.
Can someone please help me with whats going on here?

[erwincoumans]

Perhaps the initial state is overlapping or the URDF is not valid.