The incident occurred shortly after 3.30 pm on Sunday when Portuguese cab driver Paulo Cesar arrived at the hospital after receiving a call for a ride from the emergency department, Valais cantonal police said.
The cab driver arrived and was hailed by a man wearing a white smock with a surgeon’s cap and mask, police said.
"A guy dressed like a doctor motioned to me to park in the area reserved for ambulances," Cesar told 20 Minutes.
"He asked me to fetch a patient who was traumatized after an accident, who he pretended was waiting for me," the taxi driver said.
The man asked the driver to turn on the engine of the taxi to ensure that it would be warm inside for the passenger.
"He even put inside a small bag that supposedly belonged to the patient."
When the driver went in search of the patient, the man decked out in doctor’s clothes jumped in the taxi and drove off, according to information corroborated by police.
The vehicle was later recovered in Martigny, police said.
An investigation into what an officer called a "singular and exceptional" case continues.