JKR site update SPOILERS

[spookedook]

No: HPFGUIDX 158935

Ceridwen wrote:
She [JKR] doesn't say he [Snape] wasn't there under the Invisibility
Cloak.  She doesn't mention where the hypothetical Snape under the
Cloak might have been at all.  So, Snape wasn't hiding under the IC
anywhere, not even at Hogwarts.

Tinktonks responds:

I think JKR is more sneaky. Ok so we know Snape wasn't under the IC at
GH but we don't know he wasn't under the IC anywhere else. We don't know
he wasn't at GH. We don't even know that he wasn't invisible some other
was at GH just not under IC.

JKR may being very shrewd and trying to get us discount a number of
theories when she has only really said no to one very specific theory!