Why can't Christians Verify Exactly Where Jesus Was Buried?

[Minimalist]

If Marcion's writings predate Luke, then why do historians think he borrowed from Luke? (Honest question. I'm not too familiar with this.)

Because early xtian writers may have been superstitious twits but they weren't stupid.  The story told by Tertullian and Irenaeus is that Marcion deliberately took out those parts which did not support his thesis that the jewish god was an inferior god and not the super god who sent Christ.  It is a very gnostic belief system and with all the other gnostics out there must have been quite a formidable opposition to the proto-orthodox ( as Ehrman styles them.) 

I suppose that the proto-orthodox view is possible but it seems unlikely for three reasons.  One, even they give Marcion credit for creating the first canon.  The idea was so good that they stole it from him and spent the next couple of centuries working up their own.  Second,  there were many more than 4 gosples in existence and the suggestion is that various isolated groups of jesus freaks had their own.  Matthew, for example, seems to be the favorite of the Ebionites, a particularly "jewish" group of xtians which could explain matty's fascination with jewish traditions and folklore.  But none of them are named prior to late in the 2d century.  Justin Martyr's First Apology written to Emperor Antoninus Pius c 160 AD does not mention any of the gospel accounts.  He does mention something called the Memoirs of the Apostles but no one knows if these later evolved into gospels or not.  Justin did know how to cite specific works:  He did so with Xenophon and Plato of all people!  Third, Justin also never heard of anyone named "paul."  This is the killer-blow to early xtian bullshit.  What was Marcion's canon?  The Gospel of the Lord and 10 epistles of the so-called 'paul.'  When the story emerges in proto-orthodox circles "paul" is the guy who brings the story to the Gentiles.  He is opposed to jewish interpretations and that much comes through in his epistles.  But xtian writers set paul in the mid first century and Justin, one of those Roman gentiles who would have been the direct beneficiary of paul's efforts has never even fucking heard of him?  No. Sorry.  That is simply not possible.  It would be like someone writing a History of the American Revolution in 1876 and not mentioning George Washington even once.  Oh, and before you ask, while Justin never heard of paul, matthew, luke, mark or john he DID know of Marcion.

http://www.earlychristianwritings.com/te...ology.html

And there is Marcion, a man of Pontus, who is even at this day alive, and teaching his disciples to believe in some other god greater than the Creator. And he, by the aid of the devils, has caused many of every nation to speak blasphemies, and to deny that God is the maker of this universe, and to assert that some other being, greater than He, has done greater works.

Justin, First Apology  Chapter XXVI