I know he's been hanging out near the window, since he was peeking through the shredded remnants of my blinds when I came back from brunch yesterday afternoon. I just hope he finds his way up there today, and leaves. Though he may decide the cold outdoors isn't nearly as nice as he expected, after a week of scratching at the window and trying to get out into it.
Of course, there's also a risk something else will find its way in, but I think that's less of a risk during the day than it would be at night. I guess I should check downstairs soon rather than leaving the window open all day, but I don't want to have him hide again.
Meantime, Charlie's tank is covered with a blanket so there's less risk of her getting too cold; her heating pads and light are all on, too, so I think she'll be fine.