Thanks for the post. Can you elaborate on your use case a bit? Do you mean you want to be able to get a link to the file in your account on the Dropbox web site just from the file ID?
Dropbox files don't have links on the API by default, e.g., unless they're shared. A Dropbox file ID uniquely identifies a file, and enables an API app to operate on a file, e.g., to download or move/rename it, etc., without knowing the path, but there currently isn't a way to just build a private link to it on the web site just from the file ID.