Tim Marr, 44, disappeared Tuesday after leaving a voicemail on his company's answering machine about business-related matters, ThinkSpain reported.
After his family did not hear from him again for 10 hours, they reported Marr missing to police.
Marr's vehicle was later discovered in the Gaspar Aguilar area of Valencia, but there was no indication of where he might be.
One of Marr's co-workers later revealed that the missing man had been contemplating suicide, at which point the National Police contacted all hospitals in Valencia. No hospital reported having a patient matching Marr's description.
Police returned to Valencia General Hospital on Saturday, and were informed that Marr had indeed been admitted as a patient on the day he went missing.
Doctors said Marr was "strangely drowsy" when he was admitted and tests found that he had overdosed on pharmaceutical drugs. Hospital staffers said they reported the patient to the duty court judge "following standard procedure" and found it "strange" that the court did not inform police.