If I remember correctly, you used to be able to actually take the magnetic material out of the sleeve and it would run in the drive.
https://www.youtube.com/watch?v=jxt5A0KJ9nw [Early CD-ROM Drives: Why Did They Require a Caddy?]
[Edit] there used to be a website, similar to bash.org, that people would submit stories like this all the time of stupid shit they were running into as a tech. Dont recall what it was. There was also and admin site, they may have been the same.