Eject invisible CD from external drive

Here's a weird one. Decided to use a years-old borrowed Epson scanner to digitize great old family photos before letting the kids take them. Everything set up - but the software installation disc I see has a very small crack near the center. Hoping against hope, I put the disc into the Apple external optical drive, which is connected to my iMac. Nothing. So, now I have a disk in the drive and no desktop disk image to drag to the trash. These external drives have no ability to inset a paperclip, etc., to manually eject (the cheapy LG optical drive attached to my wife's iMac does still have the hole - I know - show have tried that one first...). Just for a LONG shot, I connected the drive to my MBPro - nope.

Is there any sort of Terminal command that would force the drive to vomit out its prisoner?

C4 is an option, but these drives are expensive...

Grateful for any help.