You have no case whatsoever.
Any document or information on a company's computer belongs to the company. In fact, I have known people that were terminated for using company equipment as their personal equipment.
Even if it was personal equipment tied into the company's VPN (you were not clear), you have no proof that anything happened. You are risking yet another lawsuit.
Again... you THINK your employer abused something ... but, by your own admission, you don't even know if it happened.
Please think about getting some personal help.

