This page: http://googleappsupdates.blogspot.de/2012/06/apps-script-in-docs-list.html says
Google Apps Script projects are now included in the docs list in Google D
This is a great question, and I would like to direct you guys to this link in the docs that explains the difference between a bound and an unbound script. I found a great script that someone shared and I wanted to make a backup of it, but could not find it in Google Drive even after saving his spreadsheet that was using the script. Turns out it was a bound script, and that is perfectly normal.
So I am either going to create a new project and copy and paste the script, OR maybe do it right by making another copy of it that will hopefully show up in all my sheets when I go to Tools>Script Editor.
(Edit) I copied and pasted the code into a new project. But before I did that: