I don't understand why there is inversion in a subordinate clause.
Jeg har TABT den?
At tabe means to physically drop something, or to lose in a game.
In this case, lost is used in the sense of misplacing something, and so we use at miste which is more general.
Why is it wrong to put nu as the final word of the sentence?
Is it wrong to say "... nu har jeg igen mistet den"?