Despite the year being quiet and incident-free, Hermione was prepared at
the Gryffindor/Slytherin match, and when Harry ended up with a broken
arm—albeit due to reckless flying when catching the snitch, rather than
any efforts of Dobby this time—she silently cast a shield charm on Harry
that caused Lockhart's spell to be reflected back upon himself, so it
was Gilderoy Lockhart who lost the bones in his arm and had to spend an
uncomfortable night regrowing them instead of Harry. Harry and Hermione
made sure to encourage the spread of the rumours of the curse on the
Defence Against the Dark Arts post, and Lockhart took the loss of the
bones in his arm as a sign that the rumours were true. The ridiculous
blowhard was so paranoid that something even worse might happen to him
that he handed in his notice at Easter, insisting that he leave the
castle as soon as the end-of-year exams were over. Minerva gratefully
accepted his resignation.
http://www.fanfiction.net/s/9552519/18/