Placeholders, free agents, locum tenens…no matter the name, a physician filling in for another physician has been a common practice (and a professional courtesy) for a long time. Physicians retire, resign, and get fired; physicians need vacation and personal time, as well as maternity and sick leave, too.
Of course, staffing shortages are the norm these days and physician turnover creates a huge expense. Regardless of why or how a physician vacancy exists, healthcare facilities have to maintain patient care quality—so they regularly hire part-time or temporary locum tenens physicians to fill the gap.