You say you wasnt driving it, was it knocking the last time you drove it ?
If yes the big ands gave up due to oil starvation , spun kept driving and the rest ..........
If it wasnt knocking then the dodgy patch up job has more weight , like pete said . Either way if the engine was recently built well i wouldnt gat tem to build mine ..
I feel sorry for you Charlie , something like that happen to me about 3 years ago. Mine a turbo spat the wheel out and stuffed the engine while someone else had the car and took it around the block, he even lost it and hit the kerb !!!