I had already done this to track down the IR but as I mentioned earlier, it is an empty wall that has a large space behind it (disused chimney) and nothing is reflecting. I just moved my TV so now all is well.
margarissa in my case i was pointing it to the top left and all of a sudden the remote stops thinking it is pointing to the top left and thinks it is pointing bottom right of the screen. I am now assuming that the sensor bar is just 2 IR LEDs on a stick and nothing more, in which case it would be inverted. For example when you do calibrate sensor bar, you move the remote down but the dots go up because if you keep your eye attached to the remote aiming where it is aiming, the sensor bar is moving relatively up when the remote aims down. If this is just showing the location of IR hotspots as the remote sees them, it could be pretty useful to track them down.
EDIT: I was aware of UV filter glass but not IR. I suppose IR is between visible light and microwaves and microwave ovens come with a filter on the window so why not :P