Since school children were being used to investigate the dead unicorn it seems that passing it off as a predator worked fairly well.
Have you ever tried to get a group of more than 5 people to keep a secret?
Harry didn't cast the patronus then, it was already active, he just moved it.
I am willing to help.
Have you considered electronic cigarettes?
Amelia Bones learns something at time x is an event happening at time x and information of that event could be taken back to time x - 6. If the information that she gets is from time x + 4 then that information could only go back to time x-2.
I had assumed that Dumbledore had destroyed the remains but posted a guard at the grave in case someone showed up.
This seems to be true for video game consoles. Possibly because good graphics make better ads than short loading times.