OMG! And you obviously did what any responsible parent would do in that circumstance. As I've never stuck my hand up a tailpipe or know of anyone who has, was the black soot you mentioned greazy? I'm imagining that any discharge from a tailpipe would also contain oil of some description and would be difficult to remove without lots of soap and warm water.
Now I wish Klein elaborated and asked VDK is they cleaned Deorr's arm after he stuck it in the tailpipe or if he was still covered in soot when he "vanished". And if VDK says they wiped his arm off or something that that, as opposed to "scrubbed" it with soap, then I think that should raise some eyebrows as being yet another false tale.