Thank you Sohaib for your reply, maybe you misunderstood my question, the record is there in the HCMWORKER table, however missing from the worker form on the Dynamics AX 2012 R3 client.
I have resolved the issue, our HR lady did transfer a worker from one company to another, however she forgot to assign the worker to a new position, therefore the worker was missing from the worker form listpage, and can't be found in order for us to assign him to a new position. What I did was navigate to Human Resources > Reports > "Worker not assigned to a positions", ran the report, from there I could find the worker we were searching for, clicked on the hyperlink and it opened the worker details form where we assigned him to a new position. Worker now shows on worker form listpage.