When opening a file through Directory Menu plugin, it does not appear in the "recent files" list shown by the Places plugin. I don't know which plugin manages that list.
The application that opens the file should handle that.
Sorry, I could not imagine, I did some tests and actually some files are added to the recent file list, depending on applications. This is quite astonishing, I always thought that the launcher (thunar, directory menu, etc) registered the recent files, and instead you have to rely on every application to implement such a feature... It will be broken forever! Thanks for your reply Bye Michele