You can tell if the restore process is still running with this command:
# psg amp_restore
If that command returns nothing, then the restore has stopped and should be restarted. If you see that it is running, then it's just taking a long time (because it's unzipping/untarring a lot of data).
Pro tip: the amp_restore script should always be run in a screen session. If you need to restart it, I would do this:
# screen
# amp_restore -d </complete/path/to/file.tgz>