Has my train ticket reservation been recorded?

After your payment on-line on www.tgv-europe.com, you will be given your 6-character dossier reference number on the confirmation page for your order.
 
For every order placed using the www.tgv-europe.com site, you will receive a reservation confirmation message whether or not an on-line payment was made.

This electronic message provides you with the details of your order as well as your 6-character dossier reference number.