More plausbile is that he was left with 34 to finish and threw the dart pictured into 17, thus leaving him with a score of 17 and no way of finishing with a single dart.
(
zoldergoose,
Mon 11 May 2009, 19:45,
archived)
This exactly.
(
Bela Lugosi's Dad,
Mon 11 May 2009, 19:50,
archived)