You have deleted the internet

In work I maintain our section of our website, using a slightly cumbersome system. I'm deleting old images and things we no longer need clogging up the system.

Today I learnt that ticking the box at the top of a list to select all in that list, and then unticking the items you don't want to be included, does not actually exclude those items from being deleted when you then press the delete button. 

I was alarmed when the 22 page list of images, media bundles, pdfs and articles went down to only 3 pages. And rightly so it seems, as that would pretty much delete our  whole web section. Now to work out how to fix this, or if I need to start wholly from scratch on the project. 

At least I noticed before pressing the 'make it so' button!