I would probably soak a small amount in ethanol/IPA/acetone, evaporate, and reagent test the leftover residue. I don't know if this is the best course of action, and I am not aware of how ibogaine reacts with various colorimetric reagents, but this is probably how I would approach the situation with any other substance.
But first, I would probably remove the specific mention from my above post of how I acquired the sample (hint hint).