When pressing the eject button the disc is moved a tiny bit and pulled back inside immediately afterwards. You can probably see only a very tiny bit if it, but that part can't be caught by regular tweezers or other tools available in a typical household. I also unsuccessfully tried some tips for removing a stuck DVD floating around the web.Instead, try to use the shutter of an old 3.5" floppy disc, and bend both ends of the shutter slightly outwards, so that the disc can easily slip between the ends. Now you have a tool that is thin enough to go a bit deeper into you Mac's slot-in drive. Press the Eject button and try to catch a tiny part of the disc with your newly-built tool. You should have a fairly good grip on the disc, and you can start to pull it out -- very slowly!
Warning: Be careful. You can easily ruin your disc or drive. When in doubt, contact your local Apple service partner.
More info, along with a sketch can be found in my original blog post.

