Why this drag&drop does not function?

hi all,
I’ve built this simple engine for Roleplaying game; it’s an engine that permits to store a coin in a backpack and retrieve it as soon as needed.
It is fully usable, but the retrieveCoin function doesn’t go, maybe because of a targeting problem (???); I’m struggling on it since a few days, can any experte coder help me please, I’m full of endless gratitude to anyone will gimme a hint :}

Functions are scattered through different layers in order to make them recognizable and have the attachCoin function well separated

fla in attachment (CS3, but AS 2.0)

thank you all in advance