System Restore does not restore your deleted files especially if it is found in your documents...

Suggestion 1:
Try to explore it using Windows Explorer.
Folder Option: Show All Files / Hidden Files

Suggestion 2:
If it was an intentional or someone had deleted it... No remedy for it but you can uses Tune Up Utilities to recover deleted files on your recycle bin but it will show you the status of that file if it is in good (can be use) or bad (corrupt) condition...

Hope it helps you...