I would point out first of all that the Bible is a very historically accurate and that the more things that are discovered, the more they end up verifying the Bible. What I find interesting about historical apoolgetics and the Bible is that things that have no other proof than the Bible, usually end up discovering something sooner or later that support the Bible.
But you can’t build an argument from ignorance. We don’t know what archeology will find or won’t find, but you can say positively that there is no contrary archeological evidence to this event.
You might also question the motives of the argument. It is something of an appeal to ignorance. ‘Because there is no other historical evidence of this event it is therefore not true.’ Well, the Bible is historical documentation just as Julius Caesar’s writings and Herodutus’ are. There is no historian that will say -‘well, this guy said there was a this event but no one has found any evidence for it yet, therefore he made it up.’ History isn’t like that. Some things people write may be embellished, and it is hard to work with that information, but there is a certain amount of reasonable doubt that supports this event. The gospel stories are very accurate to describe the historical events that surround the other stories, so it is likely that these things are true too. Instead of focusing on the things that we don’t know about, focus on the things we do. The crucifiction and resurrection for example, are some of the most historically reliable events in ancient history. I am unfamiliar with catholic resources for information, but I know that of some great protestant writers who have discussed the historical reliability for the resurrection. Gary Habermass is probably the leading expert and has written huge amounts on this. The Case for Christ by Lee Strobel is a very approachable work that develops the historicity well. Argue about the central points, don’t let them bog you down trying to prove extemporaneous issues.
Peace in Christ