Thanks guys. I was hoping there was some kind of backdoor.
Have any of you done backup/restores with your iPhone 4? My replacement does not have any prox-sensor issues (my original one didn't either) and I have heard restoring could be a cause for them.
*On a completely unrelated note the black color on my replacement is definitely not as dark as my original. Sitting here at work I can clearly see my prox sensor and the black is not as deep as it was before. I looked and looked at the old one before heading off to the Apple store and could not make out the prox sensor. 83027 here.