Adding node to syntax tree adds a child but it doesn't actually show up

Question

I am writing a VSPackage which needs to change a class to return the correct value according to the test. Simply changing the return value was easy, but now I am trying to add an if-else statement so that the class returns different values depending on the input:

var node = new IfElseStatement
{
    Condition = new BinaryOperatorExpression
    {
        Left = new IdentifierExpression("parameterName"),
        Operator = BinaryOperatorType.Equality,
        Right = new PrimitiveExpression(3)
    },
    TrueStatement = new ReturnStatement
    {
        Expression = new PrimitiveExpression(9)
    }
};

//Visitor finds the beginnning of the method (first child is '{' so insert after that)
var parentNodeToInsert = _abstractSyntaxTree.AcceptVisitor(new FindBeginningOfMethodVisitor());
parentNodeToInsert.InsertChildAfter(parentNodeToInsert.FirstChild, node, new Role<IfElseStatement>("Statement"));

If I put a breakpoint after this and inspect parentNodeToInsert:

Under the children of parentNodeToInsert (blue box) it has been added correctly, however the summary of the node (red box) does not contain the new if-statement, and later if I call toString() on the syntax tree (to write it back to file) it doesn't appear either.

Does anyone know why, and how to make it appear?