Ah yes, I had forgotten about gpart and testdisk. They will suit your scenario.

What kirol suggested would work, but alternatively you may want to try testdisk. Testdisk is on Knoppix and is used for recovering deleted partitions. It automates what you would otherwise need to do with cfdisk. Testdisk is easier because it has an interactive interface with step by step prompts and menus.

Simply go to the root shell and type testdisk. When the menu starts up, select the drive you want testdisk to work on (hda) and the partition type (Intel). Then select analyse.

Testdisk will analyse your disk for deleted partitions and then report what he has found to you. If you think testdisk has correctly scanned and guessed the size of the deleted partition, you may then choose to ask testdisk to proceed and write out the new partition table.

When testdisk is done, hopefully your partition has been recreated. You can then reboot and mount the partition.