It would have been better not to disable the account and check for any processes it was running by using "ps aux | grep http" and "lsof -p PID#" but now it's been disabled and that information won't be available. At this point, it's going to be far more difficult to track it down if someone else created it.
Did you remove the user entirely or just disable the user? Because if the user exists, you could check for files and folders owned by that user:
Again, if you've removed the user, that won't be available either.
At that point, you can only check /root/.bash_history for possible indications of that user being added.