canon af35m - what is the loose piece here?

[mc1801]

Hi, this is my first ever post so apologies if this is in the incorrect forum!
I have been using this canon af35m for a while and had great results from it, until recently I got back a roll of film which was entirely blank. I am sure this was due to my own loading errors, these things happen. However, I also noticed that this pale grey sheet where the window is , possibly the light sensor window, is loose and rattles around. Since noticing this, I have been wondering was it really me loading the film wrong or did this broken piece overexpose my photos perhaps? I am testing a roll of film now making sure to shake the piece back into place, but this is not a feasible way to use the camera as it takes a good minute to delicately get it in position. Also, I'm not even sure if it has any impact on photos.

Would anyone be able to tell me what this is and if it's important, or can I just keep shooting with it loose and not entirely covering that window? Also, I would be grateful if anyone knows how to put it back into place, I tried dismantling the camera with no success.

Thank you.