Here's the deal ... law enforcement officials tell us they responded to a call of an abandoned vehicle sitting in dirt just feet from train tracks near the Miami Airport Station in Florida at around 5 AM on Sunday.

According to officials, the car -- a silver Mercedes-Benz G-Class SUV with Maryland license plates -- was registered to Diggs.

But, authorities say there was no indication of the Buffalo Bills receiver, a driver OR passengers on the scene ... so after a short investigation, they simply had the vehicle towed.

The entire situation is bizarre ... especially given the Mercedes' six-figure price tag -- but when we reached out to Diggs' camp for comment, they had a simple explanation.

According to a spokesperson for the wideout, Diggs was not in Florida at the time, and had lent the car to a friend in the area.

That friend, the spokesperson said, got a flat tire, called for a tow, but did not wait for the company to arrive and left the ride at the scene.

"[Stefon] was not driving the car," Diggs' rep says. "He allowed a friend to use the car while he was gone. Unfortunately, the friend had got a flat tire with the car."

The rep says Diggs was eventually informed of the situation and is now having the car repaired at a Mercedes-Benz dealership.

Diggs' spokesperson was adamant the car was NOT stolen, and added there was absolutely no wrongdoing involved in the incident.

Cops, meanwhile, say a report on the abandoned car is still pending. It's unclear if police are investigating further into it.