Colour me perpetually naive if you wish but I saw nothing sexually in that passage either as a child or as an adult. I'm still in shock from people here seeing it as so obvious :)
I more subscribe to your theory of Foley being reckless; pushing the boundaries of what he can get away with for his own amusement.
Quite honestly, his stopping for Selby is unusual enough to stick in Selby's mind, let alone whatever Foley might say to him on the journey.