CMA Argo
From Halopedia, the Halo wiki
The Argo was a UNSC scout ship. Though small, it was equipped with a Shaw-Fujikawa Slipspace Drive.
It sent to the Harvest system in 2525 after the UNSC lost contact with that world. It sent a signal back informing the command that it had dropped out of slipspace but after that nothing was heard from it. It is assumed destroyed by the Covenant cruiser later found in the system by the UNSC Heracles