Someone stole the body!

[Angrboda]

Another possibility is that they did make some sort of deal to give Jesus a proper burial. However after negotiation with Jesus' friends, later on the deal fell through and they never allowed Jesus that burial. But nobody told the friends of Jesus that the deal was kaboshed and there would not be a body in the tomb. So when they went to the tomb in the morning, the stone was rolled away and the tomb was empty.