Do you use any cleanup or optimization programs that might delete restore points?
I create system backup images using programs such as Acronis or Macrium.
imho backup images are more reliable than restore points.
You can control how long to keep the backup, what to include and when to create the backup.
I know this doesn't help with your immediate problem, but it's something you should consider and learn to use going forward.
A couple of tutorials about imaging: Imaging with free Macrium Backup Complete Computer - Create an Image Backup
You can also take a look at the Sticky Threads in the Backup and Restore SF forum.