I'm just in the process of adding in the OctoPi camera (will it ever end? and are we nearly there yet? are constant thoughts at the moment), and something glinted as it moved on the table. It looks like I have a piece of the printer farm with me. Richard Horne's glass removal technique seems also possible with Edge.
Oh no! I guess that PET really has a strong pull. Curious, was the glass completely cool when you popped it off?
My guess is that it was printed weeks ago, so it was stone cold. This was a part shipped with the box. If you don't recognise it, you didn't get the camera upgrade. Having read the posts from Richard Horne, I fiddled with it only briefly before just leaving it. Fortunately it's not in the way at all.