Adventures with Hedgehog

This cute hedgehog has been living in our compost bin for several weeks now. Always she or he would be curled up in the corner. I thought s/he was hibernating - do hedgehogs hibernate? - and we were being careful not to smother her. But tonight I when I visited she was up wandering around on the vegetable scraps. And not too bothered that I was peering in with my camera.

The bin is one of those upright plastic ones with a lid. And I can't work out how she got in. The air vents are too small even for a small hedgehog. There is no obvious entry point. The question is: how will she get out? Is she trapped in there waiting to be rescued? Or has she found a really good place to hang out until spring?