Insospechadas translates to "unsuspected" or "unimagined." It's a less common but very descriptive word that adds a layer of mystery and wonder.
In "La Moneda," the singer uses it to describe the "alturas insospechadas" (unimagined heights) to which the person they're singing about flies. This word beautifully conveys the idea of someone reaching unexpected and perhaps dangerous levels, making the listener curious about the metaphor of the coin.
A coin is still in the air, and that is the whole problem. Vagón Chicano open on "Eres una moneda en el aire" (You're a coin up in the air) and then spend the song standing underneath it, waiting to see which way she lands. He has been at this a while and knows exactly how it goes: "Siempre he querido atraparte / Y no te dejas tocar" (I have always wanted to catch you / And you don't let yourself be touched).
What makes it better than ordinary pining is that he is frightened for her rather than only sorry for himself. She has climbed somewhere he cannot follow, and he says so plainly in "Te veo volar y me espantas / Porque te puedes caer y matar" (I watch you fly and you frighten me / Because you could fall and be killed). By the chorus he has given up chasing and simply parked himself below, with "Tarde o temprano tendrás que bajar" (Sooner or later you'll have to come down), which reads as patience or as stubbornness depending on your mood. The sharpest moment is the quietest: "Tú no perteneces a ese mundo irreal / No sé quién te dijo que era de verdad" (You don't belong to that unreal world / I don't know who told you it was real). He is not pleading there. He is telling her somebody lied to her.