Kevin Murray, aged 46, was preparing for his role in the killing the following day, a warrant for his arrest submitted by the authorities claimed.
Mr Murray was refused bail by a judge in the North. He is sought on suspicion of murder and firearms offences and is fighting extradition after he was arrested in Strabane, Co Tyrone, this month.
David Byrne, aged 33, was gunned down and two others were injured during last winter’s attack and details of the warrant for Mr Murray’s arrest were disclosed by Patricia Smyth, the recorder at Belfast court.
She said: “The requested person stayed overnight at the Regency Hotel on 4 February 2016.
“The warrant alleges that this was in preparation for his role in the murder the following day.”
The warrant also claimed Mr Murray had been identified in security camera footage of the scene by several police officers on both sides of the Irish border.
The senior judge said the severity of the offences alleged against the accused, of Townsend St, Strabane, was relevant to the decision not to grant bail. She also based her ruling on the ability of the prison service to care for his health needs.
He walks using a mobility aid and has undergone brain scans after his health degenerated in recent months, lawyers told the court. The accused is unemployed and separated from his wife.
The judge said detailed evidence was contained in the European Arrest Warrant issued by Irish authorities.
She remanded him in custody, with the case to be reviewed later this month.