You can hear children get out of bed and sneak to a sibling's bedroom, so the chances of missing the fact that there are two of the blighters hiding in the loft (specially in such a tiny house) are slim to none. And that's without the things already mentioned, such as the loft ladder, the bathroom facilities, the missing food and so on.
I'm pleased he's been found, though. I don't like storylines about children in distress.