I think the answer here is simple... Band of Misfits "play this as if" instructions expects the Band of Misfits to be in play, because that is the normal place that a card is when you are following its on-play instructions. Band of Misfits is not in play, therefore the "play this as if" instruction can't find it to move it.
Keep in mind that the reason Lose Track exists it that you can literally lose track. If a card has been moved, we can't act like we can know where it is, even if we in reality do know. Maybe it has been shuffled into a hidden pile somewhere and there's literally no way to find that same copy of that card again.
It's the exact same reason that Throne Room on Mining Village won't let you trash it twice to get +
twice. The second time you are playing it, when you get to the "you may trash this" instruction, that instruction expects that Mining Village is in play. If Mining Village is not in play, then you can't find the Mining Village in order to trash it. Again, maybe it was shuffled into a deck somewhere. We don't know where it is.