Can't be done. That's why if you ever outline something you think there is a minute chance you will need again, you need to save a non-outlined version as well as an outlined version. If you received artwork that was outlined, most likely it was to avoid any font issues, but it is also a security measure so that original text cannot be edited.
Your best bet is to try to replicate it as closely as you can with text. www.dafont.com is a great place to go to try to find matching fonts.