ERROR File not found

gistfile1.js

var mongodb         = require('mongodb')
  , Db              = mongodb.Db
  , Server          = mongodb.Server
  , ReplSetServers  = mongodb.ReplSetServers;

var mode = process.argv.slice(2)[0] || 'server';

var mongoConfig = {
    replset : {
        servers : [
            { host: 'localhost', port: 27017, options : { auto_reconnect: true, poolSize: 1 } }
          , { host: 'localhost', port: 27018, options : { auto_reconnect: true, poolSize: 1 } }
          , { host: 'localhost', port: 27019, options : { auto_reconnect: true, poolSize: 1 } }
        ]
      , options : {
            rs_name         : 'rs0'
          , read_secondary  : true
        }
    }
  , server : { host: 'localhost', port: 27017, options : { auto_reconnect: true } }
  , options : {
        safe  : { w: 'all', wtimeout: 5000 }
    }
  , db   : 'test-replset'
};

function createServer(serverInfo) {
    return new Server(serverInfo.host, serverInfo.port, serverInfo.options);
}

function createReplicaSet(replsetConfig) {
    return new ReplSetServers(replsetConfig.servers.map(createServer), replsetConfig.options);
}

function connect(callback) {
    var replset, server;

    if(mode == 'replset') {
        replset = createReplicaSet(mongoConfig.replset);
    } else {
        server = createServer(mongoConfig.server);
    }

    if(mongoConfig.options.safe && mongoConfig.options.safe.w == 'all' ) {
        mongoConfig.options.safe.w = (replset) ? replset.servers.length : 1;
    }
    
    var client = new Db( mongoConfig.db
                       , replset || server
                       , {safe:true } );
    client.open(function(err, db) {
        if(err) {
            console.log(err);
            return;
        }
        console.log(err || "Connected to MongoDB");
        callback(null, client);
    });
}

function success(doc) {
    console.log("success!", doc);
}

function error(err) {
    console.log("ERROR",err.message);
}

connect(function(err, db) {
    db.collection('files', function(err, files) {
        files.remove({}, function(err) {
            if(err) {
                error(err || new Error('Error emptying collection'));
                return;
            }
            for(var i=0;i<10;i++) {
                files.insert({servername: "hello"+i, originalname: "world"+i}, function(err, docs) {
                    if(err || !docs) {
                        error(err || new Error('Error inserting file'));
                        return;
                    }
                    files.findOne({servername: "hello"+i}, function(err, doc) {
                        if(err || !doc) {
                            error(err || new Error('File not found'));
                            return;
                        }
                        success(doc);
                    });
                });
            }
        });
    });
});

output is :

Connected to MongoDB
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found
ERROR File not found