The website that has been transferred online represents a fraction of the complete project (html and javascript with css format). It cannot be opened by Web Creator. 

To modify a website, you must have access to the complete project file (extension .LWC and .pag format pages). If it was lost or destroyed, you will unfortunately have to rebuild your website, but you can save a lot of time by doing copy-paste of images from the online websites. 

Solution: 
Make regular backups of your complete Web Creator project. You can use it to save a backup on an external disk, USB key, CD or even directly on your hosting server is the disk space allows.