Trace Adkins -- Happy Trails, Rehab

Trace Adkins beat a hasty retreat from rehab -- just 14 days after he entered the Florida facility for alcoholism ... TMZ has learned.

Sources connected to Trace tell TMZ ... the country star's father is seriously ill and he felt he needed to be at his bedside ... immediately.

We're told when the illness resolves itself ... Trace will then decide if he goes back to an inpatient program or does outpatient therapy.

As for his immediate sobriety, we're told Trace asked his therapists in Florida to put him in contact with counselors near his dad.