Nano-biomimetic ship organism:
The ship can last virtually forever, because it regenerates like a living organism. There is no point in removing the dirt, because the dirt is irrelevant. Far be it, the ship may be intelligent and know the dirt is cover. But it has programming and instructions, and it simply doesn't need to do ANYTHING until the conditions of it's programming are met, other than survive. With essentially infinite power, and assumedly the ability to obtain raw materials from anywhere (groundwater has minerals, elements, etc.) why would a ship ever move?
Since the ship can be treated like a living metallic organism, it heals, regenerates and fulfills all it's needs like a plant or animal.Some plants have lived over 5000 years. Some clonal organisms are believed to be over 80,000 years old. But plants and animals have things that can eat them, and they need to obtain energy. Since it's needs are so incredibly humble (it doesn't need energy and can mine everything it needs) it could in theory last for hundreds of thousands of years until somehow all multiply-redundant systems somehow accidentally fail at the same time. While nothing lives forever, there's no reason this thing can't "live" for a mere 30,000 years.