Scott, 17, who is autistic, was left in a critical condition after he was repeatedly kicked in the head during the attack last week.
Police said a 17-year-old boy was arrested on suspicion of attempted murder on Thursday.
Officers also searched an address in Ashmount Gardens in the Hillhall Estate.
Police said they removed a number of items for further examination.
Scott had been missing for more than 24 hours when he was found by a police dog handler last Friday night.
He was discovered lying unconscious in the grounds of a disused furniture showroom close to the Lagan towpath.
His mother had raised the alarm at 22:00 BST on Thursday after he failed to return home from college.
Scott is a student at the South Eastern Regional College in Lisburn where he also attends a job club, run by the learning disability charity, Mencap.