BubbleHead Charm (was Beedle the Bard SPOILERS\Animagi comentary)

[pippin_999]

No: HPFGUIDX 185194

Jerri:
  In fact, it could even have been 
> in one or more of the books HRH had looked through, but they were so
focused  on "water" that if the charm was not described with the word
"water" in a prominent enough part of the description, they easily
could have missed it.

Pippin:
Nothing in the rules prevents you from checking out or hiding with 
charms any books that might be useful to your opponents. I always
assumed that the other contestants, who had a head start on Harry, had
done so. Besides that, while Hermione has a broad range of interests
and is excellent at retaining what she reads, she has one weakness as
a researcher -- she's not creative. It never occurred to her to look
through Ron's chocolate frog cards for mention of Nicholas Flammell,
for example.  

Inconsistencies are inevitable in a work of this kind -- but the trace
isn't one of them. We've known since CoS that the Ministry had some
way of detecting magic that's done around underage wizards and that
they couldn't seem to tell who was actually doing it. We just didn't
know what it was called. 

Pippin