Nobody had to worry about tipping off anyone after the attack. During it they knew they were being watched. I bet you can find a shot of one of them flipping off the camera in the sky.
I agree, the excuse that they deleted the information to keep it classified because they were tracking the Al Qaeda groups is BS. I heard that they were indeed tracking the Al Qaeda group, they were tracking them because they had information that some of the weapons that the US had supplied to Libyan rebels were in the hands of the Al Qaeda group.
There was no need to keep it a secret because the Libyan officials had been saying it since before the attack began. Even if the Obama people did want to keep the Al Qaeda connection a secret, that doesn’t excuse the lie about the video and the peaceful protest. It just doesn’t follow.