Well if you're using a videotron routeur, technical support should be able to reset your admin password remotely. (they cannot see what it is tho)
The other thing that comes to mind would be to format the routeur entirely. Usually done by holding the reset button in the back with a pen for roughtly 20-30 secondes. This will erase any and all configuration you have done to the device and bring it back to it's default values. (A videotron routeur has these infos on a sticker in the back of it)
Otherwise, I don't really know of many other ways to retreive it.