Depending on how the animation is done, you can get surprisingly long playtime from small files. But this sounds like they're using a flash player to dynamiclally stream content from somewhere else. Google does this for their video site. Unless you can disassemble the flash to figure out where the media is actually coming from, you're probably screwed.

If it's not animated, then it's definitely not a "flash movie". It's a movie in some other format (mpg, mov, wmv) wrapped in flash controls.