the real culprit to my problems:

Where did you find the magnet?

Some suggestions on where to easily source a replacement would be a big help to some people too.

My idea is to go to any general store/hardware store and purchase one of those rubberized fridge magnets and cut a small enough piece off with a sharp craft knife, then just fashion it to shape and size.

Just noticed this is already mentioned earlier in the thread

In a similar vein. Whenever I've been giving my 900 a bit of a clean and brushed my finger over the recess near the camera lens the handset has buzzed, as if the lens cover has been opened, so I think the camera relies on both the optical and magnetic sensors working.

I haven't searched or read up on it, but yeah, my impression was that fcam has a "feature" where if you were using it the last time you had the camera lens open, it prevents the camera app from starting automatically the next time you open the camera lens. Though I haven't tested to see what magical steps truly makes that happen, it seems like that'd be really convenient for those that regularly use fcam over the default camera app.

Either way, manually starting the default camera app seems to reconnect it to the sliding cover action again for me (at least up until I use fcam again). Keeping shortcuts on a desktop for easy access to both apps relieves most of the pain if you do use both apps.

A thick fridge magnet will do. A thick enough magnet that's easy enough to cut with a box cutter shouldn't be hard to find.