If the Resurrection hadn't actually happened, wouldn't we see some proof of it after all this time?
They'd have found a tomb or a burial plot for where Jesus' body had really gone. Or if His body had been burned, there'd be some record of it, somewhere. Somebody would have eventually admitted it. One of the Apostles would have ratted it out.
After all this time, there'd be some proof of what had really happened to Jesus' body, if the Resurrection wasn't true.