Assuming you`re on a Mac.
If not I have no idea how to help you..
Go into finder..
hit shift/command/g
A search box will pop up.
Copy/paste this line into it..
~/Library/Application Support/MobileSync/Backup/
Finder will take you directly to the iPhone back-up file.
It`s called "Back Up" and in it is another folder with a lot of digits in the name.
Inside this folder are the back up logs which are a time consuming pain in the ass to read.
From there you`re on your own.
At this point it`s sifting through a needle looking for a haystack.
Someone else might know of a viewer to decode the actual text files/logs.