How can I tell if the state is accidentally e-filed so I don't double file by sending in paper?

I wanted to paper file on this taxpayer, but I think I accidentally used my one free state e-file.  How do I verify if I did or not?  The Turbo Tax cover sheet when printed for review said mail in instructions.  Now that I e-filed federal, the state cover sheet says electronic instructions for this taxpayer.  How do I verify whether his state form was e-filed to avoid double filing?