The auto rewinder on most point & shoots has a sensor to detect resistance to the rewind motor. If it does not detect any resistance the winder will stop because it assumes the film has been completely rolled back into the cartridge.

If you do shoot a roll of film and it doesn't rewind, there's still hope for the images you shot. Get in a completely dark room with absolutely zero light visible under a door or any other opening. Any light at all will fog your film!

Working by feel, open the back of the camera, remove the cartridge, gently pull the cartridge away from the camera to unroll the film from the camera's takeup spool. You may want to pinch the first half-inch or so if the film where it comes out of the cannister. Avoid touching any other part of the film, as your fingerprints will be impressed onto the film. If you must touch the film in the middle of the strip, do so at the extreme edges only. There is about 5mm (roughly 7/32 inch) on each side of the strip that is not part of the image area.

Once you have the film free of the camera, using the nipple on the end of the cartridge that normally engages the camera's winder, use your fingers to wind the film back into the cannister.

You may find a pair of needle nosed pliers helpful to turn the nipple, or a flat piece of metal such as a narrow file that is just narrow enough to fit inside the nipple but wide enough to engage the two nubs inside. You can check the fit of any tools under light on another film cannister that doesn't have the film pulled out yet. But you'll have to do everything by feel in total darkness with any film that is out of the cannister. Latex gloves may come in handy to help prevent getting fingerprints on the film, but you can still leave smudges, even with gloves on.