Mobile Banner Images Recently disappeared

Quick question for the forum. I use version 7.0. I'll update to 7.1 later but currently I'm just trying to get my site out and am in the home stretch. I realized last night that the CSS I had created for each of the page banner images for mobile view no longer functions. The code hasn't been tampered with...but it's now saying that none of the images actually exist. Which seems to be the case. None of the images I used for the CSS mobile banner code are in the library. They're just gone. Soooo....I've gotta figure that out because the banner images on my site DO NOT translate well at all to mobile. But literally every single page's mobile banner is just not there any longer. My plan is to leave the code and just run the process again and replace each image url with the new one. But I def don't want this to happen again as it's super time consuming.

The only thought I have about it is that maybe since those images are used nowhere else on the site and were only used briefly to collect the urls that maybe they didn't save? They were all there for about a week though. Just confused on what happened and how to avoid a re-do.

I was thinking a good idea would be to save the images in an inactive page as image blocks so that they're still somewhere on the site. Is that a good idea?

I'm just not sure why they vanished. Images that are no longer used that have been on the site for years are still in the library. 

Anyway, any help or guidance would be appreciated. With the exception of copy edits on one page...when the mobile headers are sorted out, I'm basically done and can FINALLY get around to marketing. Thanks!

Hi,

What is site url? We can check easier