The Missing List gives the date of "Thomas Downey"'s disappearance as 24 Apr 1921, I think that this is the same man as Thomas Downing who disappeared 24 Nov 1921. And that it is a mistake in the list
Downing was an ex-soldier and the son of an ex-RIC man. He was kidnapped while going to a Discharged Soldiers’ and Sailors’ meeting on Tuesday 23 November 1920 according to Cork Examiner. Immediately after his disappearance a notice was circulated in Cork: ‘Kidnapping in Cork. Notice. If Mr Downey [sic] is not returned to his home within 56 hours, Cork citizens prepare, especially Sinn Feiners. Black and Tans.’ He worked as a civilian telegrapher for the Royal Engineers at Victoria Barracks
There is a report from Florrie O'Donoughue to the IRA's Adjutant General that Downing had been convicted and shot was a spy. But there are no Witness Statement, and Downings body has never been found, so no death certificate