He put his foot in the bidet? Gross!I think it's not easy to reconstruct every detail when we don't even know what was the position of the bathmat at that moment.
IMO it's possible that the bathmat was in other position or that Guede used the bidet to clean his pant leg.
ETA: Of course you're wrong about the print being complete. I'm referring you to the photos Otto posted in previous thread.