How did levicorpus leak?

[Nicolau C. Saldanha]

No: HPFGUIDX 162011

Sorry if this has been discussed already, but here is my question: how
did levicorpus leak? I mean, young Severus Sanpe invented it, wrote it
down on his potions book and next thing all of Hogwarts knows the
spell but they do not know who invented it! At least, that is what
Lupin tells Harry and I cannot imagine why Lupin would lie about it.
So, I do not believe that Snape showed everybody the new spell he had
just invented during a class or something. Since the spell in
nonverbal, other students could not even had learned it by imitation.
Thus, either Snape told some unknown student X about the spell or X
examined Snape's potions book long before Harry did, and X then passed
Levicorpus on to other students without explaining how he or she had
learned about it.

It is of course perfectly possible that the author does not care about
the identity of X, but I have a theory: X is Lily Evans. This explains
a lot in the "Snape's worst memory" pensieve scene: why Lily
interferes, why Snape is angry at her. It is also possible that
Slughorn is more right than he imagines when he says that Harry is as
talented for potions as his mother was: maybe she learned something
from the very same book.

What do you think?

Nicolau