iPhone NSURLConnection download file logging

Situation:

Application downloads very small file every time it starts. IIS7 server logs keep track of this 开发者_StackOverflow中文版file.

Problem:

Server doesn't log every download (unless 50% people downloaded app and didn't even start it).

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What may be the cause? Could it be that iPhone users from some area use proxy instead of connecting to my server every time?

How to solve it? Is there some kind of request I can make (and how?) so that users always download the file from server? Or some other way to make IIS log every file transfer (possibly without changing anything in IIS setup).

Thanks in advance!