I was at a session the other night and two blokes played a jazz tinged blues on guitars. I struggled to join in (partly because I couldn't see their playing) and so at the end I asked the nearest one what key they had been in. He replied, to my astonishment, and quite sincerely, that he didn't even know the names of the strings of the guitar, never mind the key.
Again, there is another fellow who accompanies himself well with a guitar played left-handed but strung normally; it takes you ages to identify even the most obvious chords.
   I find this kind of thing fascinating in that it would almost be easier to learn in an orthodox way.
   Anyone have similar examples?