I have a web app solution which has many projects, and 5 of the projects within it contain a file named Cig.SF.ClientLib.dll.config. When I open the solution in VS 2012 (Update 3) and I type "Cig.SF.ClientLib.dll." (without the quotes) into the Search pane, there are 5 files reported; but when I open the same solution in VS 2013 and enter the same search text, sometimes only 1 file is found, sometimes more are found, but so far, never all 5.
I have tested this behavior in the same solution with other filenames, and see similar behavior - more files are found by VS 2012 than 2013. I can provide screenshots to show the condition (which I will attach to the issue), but I have not yet tried to reproduce it with new solutions/projects, due to the time and effort required.
I'm not sure if it matters, but some of the projects target .NET 2.0.