Main bearings are on the crankshaft into the block.

Rod bearings are....for the conrods.

Post a picture of the bearing. In extreme cases, the bearings can get crushed, mangled, destroyed so yes there may only be one bearig left, or it might have spun and melted itself into the other bearing.

But if a bearing has spun in the rod, the rod MUST be replaced too, or it will fail again very soon after. Some people say they might be able to repair the rod, re-size it etc...I'd go for a new rod.