Mongoose findByIdAndUpdate not pulling
<p>I am trying to pull an object from a subdocument in a mongodb. The structure is as follows (from <code>db.users.find().pretty()</code>):</p>

<pre><code>{
"_id" : ObjectId("56a660b42819b770b89950bd"),
"userName" : "someGuy",
"itemCollection" : [
    {
        "item_name" : "item1",
        "_id" : ObjectId("56a661232819b770b89950be")
    }
],
"__v" : 13
}
</code></pre>

<p>This code:</p>

<pre><code>var userID = req.user._id;
var transactionID = req.body._id;
console.log('userID: '+userID);
console.log('transactionID: '+transactionID);
User.findByIdAndUpdate(
    userID,
    {$pull: {'itemCollection': {'_id': transactionID}}},{new: true}, function(err, model){
    if(err){
        console.log('ERROR: ' + err);
    }
    console.log(model);
});
</code></pre>

<p>Gets me the following output:</p>

<pre><code>&gt; userID: 56a660b42819b770b89950bd
&gt; transactionID: 56a661232819b770b89950be
&gt; { itemCollection: 
    [ { item_name: 'item1',
    _id: 56a661232819b770b89950be } ],
__v: 13,
userName: 'someGuy',
_id: 56a660b42819b770b89950bd }
</code></pre>

<p>So nothing seems to have happened. I've tried every variation on stack overflow that I could find but it never deletes it. Does anyone see what is wrong?</p>