Maybe something along the line of ... Hi Name, Regarding the ArticleName that you quoted me. I've noticed there's no link to my Company for your online version. Can you help me out and link my company to that article? It would mean a lot to me.
Then if they say no, ask how come, then tell them that they used your time and help them with their content - it will be a good business relationship with them if they return the gratitude and simply put a link for their online version.
If they still refuse, then tell them thanks for the time, and you will be available for what ever services you provide. So just keep promoting yourself, and get your company in their mind, but don't be hard on that issue. At least you know why they didn't link you.
Let me know how you go. Just ask nicely I recken.