Over the years in talking with employees there were several times when an employee would came to me and told me they were not happy with their position. I would find out what was wrong and then asked if they had told their manager and/or supervisor. Nine times out of ten the answer was “I assume they know.” My response was “how would they know?” If the employee is doing a good job not complaining and coming to work every day on time why would anyone think there was a problem?
Managers and/ or supervisors are not mind readers unless you send out specific signals such as your work is sloppy; you are late all the time, etc. Even then they may not realize what the problem is and assume your work ethics are sliding. They have their own set of issues to deal with on a daily basis and as long as things are flowing smoothly the manager and/or supervisor have no way of knowing.
So the solution is to keep the lines of communication open. If something is bothering you with your position whether it is the workload, a co-worker or perhaps a promotion you felt you deserved, talk to your manager/supervisor. They won’t know until you tell them and maybe there will be a good solution and outcome.