What's missing is a bass clef at the end of the 4th bar/measure before 17 - there's just room for it in it's correct place, in both the solo part and the piano part. Any student of Prof Devemy's at the Paris Conservatoire would have been able to play the low A as well as he could play the low B 8 bars earlier, or else he wouldn't have been entered for the Concours!