Hello chokzi,
I am a Nero employee and would like to help you.
If you have Nero RescueAgent installed, you can use it to recover data from multisession discs in case you forgot to add the existing content to your last session or in case something went wrong during that process.
Simply open Nero RescueAgent, select the drive that contains the disc you want to recover from and choose the scanning depth (a fast scan should be sufficient). If you press Next, the next screen should show you the data found by RescueAgent. Tick the checkboxes next to the files / folders you want to recover, select a target destination and let RescueAgent recover the files.
If you need further assistance, feel free to contact our support (http://www.nero.com/enu/support-form.html) or visit our community (http://my.nero.com/).
Best regards