Pretty much my take
Although i always thought the theory on them medicating the kids to sleep could've been a plausible one. I mean leaving the kids alone is a crazy thing to do, but I'm certain they wouldn't have want kids to be awake roaming around an apartment. They are doctors and maybe they thought they could safely medicate them to be fast asleep while they were out getting sloshed. Then maybe something went wrong doing that. That part is not far fetched at all, but then could they really cover their tracks so well from that point? I dunno.
I'm pretty certain she wasn't snatched by chance though. If it did happen, someone's had their eye on them for a bit. I mean if it was just a chance, it's somewhat unlikely they were just gonna climb into a random hotel room window or whatever, there could've been 3 blokes sat in the room. I fight it highly unlikely someone out to snatch a kid just happens to find a random apartment by chance with a kid on their own while their parents were out on the razz. If she has genuinely been taken, it's likely by someone who has done their homework.
maybe we'll never find out but something always felt off about the whole thing.