The tomb was closed by a large stone and guarded by Roman soldiers, soldiers who would imperil their own lives if they abandoned their post.
Removing the body in such a situation is only easy to do in the fantasies of the atheist true believer.
That is another thing: The gospels disagree on who was guarding.
Mark:
No guard
Matthew:
The Pharisees went to Pilate the day after preparation. Pilate said to them, “You have a guard; go, make it as secure as you know how.” 66 And they went and made the grave secure, and along with the guard they set a seal on the stone
Luke
No guard.
John: No guard
No Roman guards.
Paul’s 1st letter to the Corinthians: No resurrection! apparently that was developed later.
http://en.wikipedia.org/wiki/The_Lost_Tomb_of_Jesus