Placing icml and get reference

app.activeDocument.place(fileToPlace)

This simply loads the place gun. As Robert said, you need to place the file somewhere. Be aware that place() returns an array of placed objects, even if you place just one item. So your code goes more or less like this:

var frame = // Some reference to a text frame
var fileToPlace = File.openDialog("Select ICML file to place", "*.icml");
var placedItem = frame.place(fileToPlace)[0];
// To embed the link, simply use itemLink: more efficient
placedItem.itemLink.unlink();

// placedItem is now a valid reference to the placed story

P.

placedItem should be your reference - but I think it's a link - so if in the next line you're unlinking it - you are destroying it? 

So you either need to place your file into a TextFrame first - or get a reference to the parent BEFORE you unlink. 

Update:

You are not destroying the link directly - but every operation on the link - destroys it automatically and creates new one in the background - that's why you need to get a reference to the parent BEFORE you modify the link.