No. No he did not. And stop being a dumbass.
There's zero logic in even speculating about this. "Oh, there could be a cover-up!" Do you have any EVIDENCE that there was a cover-up? Lack of information is not evidence FOR something. It's just a lack of information, probably because Scalia's friends and family don't want a giant media circus over his death, which, from the very first report, was pretty evidently going to happen.
But, by speculating that there "might be a cover-up", you're declaring two mutually exclusive and thus stupid things.
1.) Obama (or his staff) is smart enough to have a major public figure assassinated AND cover it up, BUT . . .
2.) He was too stupid to do it at the beginning of his first term when he'd be guaranteed to be able to appoint Scalia's replacement.
THINK about that for a second. If you're going to off someone and then cover it up, the DUMBEST POSSIBLE TIME to do that would be to time it during a hotly-contested election campaign when it's INEVITABLY going to be come the Story Of The Year. The point of a cover up is that you DON'T want the entire friggin country breathing down your neck while you're trying to bury the evidence.
Use some friggin sense, people.