In this case, I'd say the photograph would be newsworthy enough to be run all over the mainstream media, and indexed extensively by Google.
2) The lack of a picture doesn't mean the two were never physically close enough to be photographed together. It just means they were never so when a camera was around.
3) It ignores the broader social context in which Google is the funnel through which information exists. If the ministry of truth wants to rewrite history, they'll do so by manipulating what Google results are available. The entire point of the article is how history can be manipulated, and then succumbs to verification via a source that can, in fact, be manipulated. That is, imagine a picture was taken, and you're sitting here thinking, "I really thought those two met." If verification constitutes, "Is it on Google?" then the task of changing history is pretty easy.
I see what you're trying to say here, but you've picked a terrible example. The probability that these men would meet and there would not be cameras around is negligible. Non-zero, I concede, but in a Bayesian world absence of evidence is indeed evidence of absence, under the right circumstances. (The conventional phrasing is wrong, it ought to read "Absence of evidence is not 100% proof of absence", which scans much less well but is actually correct; the phrase is intrinsically Aristotelian.)
The historical fact is that these two have never publicly met. They already were pretty certain they knew this, but checked google just to be absolutely sure. Doing an image search is a lot easier than doing a text search since there's an awful lot of articles which mention them both and it would be too hard to sort through the guff.
That doesn't mean you can fool people into thinking that something never happened just by removing all pictures of it from google image search. (Removing pictures would of course be a necessary but not sufficient step for anyone wanting to remove something from history.)
If Obama and Ahmedinajad decided to meet, it would certainly be something Obama wanted to keep out of the newspapers. I certainly think that it is within the power of the President of the United States to arrange a secret meeting.