You've probably checked this already, but bear with me:
Unless the file haven't been moved somewhere else on the phone for some odd reason (i.e. a directory which isn't accessible to your PC) I would look into file permissions and video container/file type (although Windows should list even "unknown" file types in most cases). It would however seem unlikely that this one media file should turn out to be different from all the others in either regard.
Other than that, some setting in Windows or iOS limiting file size perhaps?