pumpkin root eater?

I have been on holiday for a week, and, despite getting very nervous on the plane back home, the garden seems to have survived more or less intact. I checked it all in the dark last night when I got in and everything looked more or less healthy (if a bit wild!)

However, this morning when I got up my whole pumpkin had gone from an upright (if smallish) guy to a droopy one (temptation for a rude joke here). When I lifted a leaf to see just how droopy the whole plant just came out of the soil - looks like it had been cut off halfway down the root. I have stuck it back in with what roots still remain but I don't have too much hope fot it.

As for why the poor thing fell, I saw a little bug on him as I was trying to fix him. It looked just like a lady bug, round and shiny with black spots - onlyit was green with a white-ish head. It didn't look like a cucumber beetle - it was rounder - but could it still be one? The plant-death symptoms are right.

If it was what can I do to stop the blighters getting at the rest of the veg? And if it wasn't then could it just be a green lady bug? What could have snapped a (quite large) root overnight?

Any advice would be grand, thanks!