title: Missing field in Mongo/Mongoose Query Results
body: <p>I am trying to publish a node app to my Raspberrypi (the closest thing I have to a dedicated server XD ) for some of my friends to test a little web-app I wrote, but for some reason one of the queries is not working correctly on the pi when it does on my ide (cloud 9).</p>
  
  <p>Here is the schema:</p>
  
  <pre><code>var campaignSchema = new Schema({
      gameMaster: {
          type: Schema.Types.ObjectId,
          ref: "Users"
      },
      players: [{
         type: Schema.Types.ObjectId ,
        ref: "Users"
      }],
      name: String,
      gameSystem: String,
      subSystem: String
  });
  </code></pre>
  
  <p>And here is the query:</p>
  
  <pre><code>db.Campaign.findOne({'_id' : req.params.campaign}, 'gameMaster players')
  .exec(function(err, campaign){
      console.log(campaign);
  });
  </code></pre>
  
  <p>Which results in :</p>
  
  <pre><code>{ 
      _id: 556f09195865094845a0d522, 
      players: [] 
  }
  </code></pre>
  
  <p>But doing <code>db.campaigns.find({})</code> in mongo results in:</p>
  
  <pre><code>{ 
      "_id" : ObjectId("556f09195865094845a0d522"), 
      "gameMaster" : ObjectId("556d1daf4b9b697213468827"), 
      "gameSystem" : "Nwodv2", 
      "subSystem" : "Demon", 
      "name" : "Baltimore", 
      "players" : [ ], 
      "__v" : 0 
  }
  </code></pre>
  
  <p>I feel like I must be missing something... I don't have any idea how to resolve this though, I tried the query without a limiter on the fields, but it still omitted the <code>gameMaster</code> field...</p>
  
  <p>Edit: at request here is the creation of the Campaign object</p>
  
  <pre><code>var campaign = new db.Campaign({
          gameMaster: userid,
          gameSystem: req.body.system,
          subSystem: req.body.subsystem,
          name: req.body.name
      });
  </code></pre>
  
  <p>To be further confounding, this query works:</p>
  
  <pre><code>db.Campaign.findOne({'_id' : req.params.campaign}, 
      '_id name gameSystem subSystem gameMaster players') 
      .populate('gameMaster', '_id displayName')
      .populate('players', '_id displayName')
      .exec(function(err, campaign) {
        //gameMaster is valid here with the id and displayName populated...
      });
  </code></pre>