I am well aware that the most probable response is "you can't", but I thought that it can't hurt to ask. Thank you for your help!
I would be suspicious of anyone that only had access to the "c2runtime.js" and not the pre-exported project, as that file can easily be ripped from the webpage.
This would generally be the case if you haven't also received the accompanying exported files.
Did you receive all of the exported files? If so, then at least you will have access to all the graphics, audio etc.