My guess is that the site receives a token from a php/asp file in the same directory as the swf that is then used as a “passkey” to see if it’s in the same directory as the php file and hence on the webserver.
At least that’s how I would do it. You’d have to decompile it and reroute the paths to get around it…
I bet it’s just a series of files that are used for the site, and you only downloaded one of them. Probably nothing as interesting as a serverside “passkey”, just multiple .swf files.