Earliest Christians who believed Jesus's body was gone did not see it as especially worthwhile evidence for Jesus's resurrection.1 (Scholars often make this point.)2 This is relevant because if they did not see it as especially worthwhile evidence, then they would not really be motivated to acquire an argument that makes use of it.
b) Early Christians felt that it was hard to establish the fact that Jesus's body was gone to persons outside Jerusalem.
• Robert Stein (citing Althaus) “...that if the story of the empty tomb arose as an apology for the resurrection, it is most strange that it does not serve this function in the accounts themselves (cf. Mk 16:8; Lk 24:22-24; Jn 20:11-15). [“Was the Tomb Really Empty?”, Themelios 5.1 (1979): online]
• Wolfhart Pannenberg (Professor of Systematic Theology at Harvard [and others]): “In J erusalem the empty tomb had to be important as a self-evident fact, but not equally so in Ephesus or Corinth.” [Systematic Theology (T & T Clark, 1988-1994), 359.]c) Early Christians felt that skeptics could explain it away relatively easy. For example, by saying (1) “…Jesus's body was simply stolen” (which, since AD 30, is precisely what critical Jews were saying), (2) “…Jesus's body was simply moved elsewhere” (which was Mary's initial suspicion, see Jn 20:2, 13, 15), (3) “…Jesus's body was simply assumed into heaven (like Elijah or Enoch).”
• Wolfhart Pannenberg: “Paul found proof of the event in the appearances of the risen Lord, not in the empty tomb. This is understandable in view of the fact that the empty tomb could be explained in different ways. … Furthermore, the fact of the empty tomb has no importance of its own if it is implied already in a raising or rising again or if by itself it cannot sustain the proclaiming of a resurrection." [Systematic Theology (T & T Clark, 1988-1994), 359.]
• Craig Keener (Historical Jesus & NT Scholar; professor): "Though the corpse remaining in the tomb would have easily publicly refuted a resurrection claim, had the authorities been able to produce it, an empty tomb by itself would not be self-explanatory." [The Historical Jesus of the Gospels (Wm. B. Eerdmans, 2009), 342.]
• Ben Witherington (NT professor at Asbury): "If it were merely the case that something happened to Jesus' body at Easter, it could have easily been assumed that he was taken up into heaven like an Elijah or an Enoch. As Gospel traditions such as John 20 make evident, an empty tomb by itself was subject to a variety of interpretations, including grave robbing. The empty tomb story by itself would not likely have generated the belief in a risen Jesus." [He Is Risen Indeed, online]
• Robert Gundry (NT Scholar, professor at Westmont): "…since emptiness does not prove resurrection and since the NT shows awareness of that fact…, Christians had only a weak motive to fabricate the story of an empty tomb." [Mark: A Commentary on His Apology for the Cross (Wm. B. Eerdmans, 2000), 995.]
Even in the synoptic Gospel traditions where Jesus's missing body is explicitly reported, it simply did not function as apologetics/evidence for his resurrection. This is relevant because if early Christians desired to use the empty tomb as apologetics, then it would sooner play the role of evidence in the gospel traditions.
Early Christians who believed Jesus's grave was empty did not much use or emphasize it in their apologetics for Jesus's resurrection. This is relevant because if Christians really cared to use the empty grave as an apologetic for Jesus's resurrection, then we sooner would be seeing reports of it used as apologetics.