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.