Node Express says EADDRINUSE But port is free

When trying to start my node express service, I am having trouble with the infamous error "listen EADDRINUSE."

Here's the line where I attempt to call listen:

var server = app.listen(3000, function() {
  console.log("listening on port %d", server.address().port);
});

The thing is, I can't find any other node process running, nor does anything show running on port 3000.

Here are the results I get for those inquiries:

$ ps aux | grep node
ec2-user  7780  0.0  0.0 110280   848 pts/1    S+   17:41   0:00 grep node

$ nestat -anp | grep 3000
<nothing>

This is quite baffling. I could try to recycle the box, but it's running a live site and I'm reluctant to do that.

Is there anything else I can do to try to troubleshoot this?

EDIT: Thanks, Ali, for suggesting the obvious thing that I somehow missed. I am now up and running on port 3300. But, when I check netstat I don't see 3300 in there either. Which suggests to me that I have some sort of process running on 3000 that I don't know how to find. For the record, this is an AWS Linux AMI.