I don't see how it couldn't be in the source file. It's likely stuffed in a .js file if there wasn't a direct variable embeded along with the .swf's url or html.
It's not like there's only one player file for each individual video on one's server, and then the video itself. With that said, if you can't embed it by clicking a share button, they've likely already prevented all but a select few servers if that, from requesting it.
JWPlayer isn't typically used by the "mainstream" companies. They'd likely do what I would, and prevent you from accessing it server-side so you couldn't screw them from advertisements or potential conversions of memberships.