Agreed - you need to let that go. I know you think that if you found that out - that you could move on, but to be frank - I don't believe it would be that simple for you. How many other things have you thought that about and then continued to want to be with her?
Wanting to know that kind of info. is just going to perpetuate the state you are in with your W. At this point, it is probably best for you to truly detach and give her true space. Not just make her think she has space - but truly give it to her.
On the other side, what do you think she would think of you if she found out you requested phone records from months back to check up on her? I think that is exactly the kind of behavior that will continue to push her away...
