You should have restored from the backup before you synced the iPad. If iTunes created a new backup when you synced, the old backup may have been overwritten and the data may be gone.
Without connecting the iPad to your computer, launch iTunes and go to Edit>Preferences>Devices. Do you see a backup in that window from the day that you backed up the iPad before you sent it out to be replaced? If you do have a backup from that days, you can try restoring from that backup. While you are still in that window, click on the box that says - prevent iPods, iPhones .... From syncing automatically. Click OK. Quit iTunes.
Connect the iPad to your computer and launch iTunes, right click on the iPad under devices and select Restore From Backup. Select that backup from the window that pops up and restore from it. Then sync with iTunes.
You can turn Auto sync back on in the prefers when you are done.