The Mullingar man returned to his homeland to fill the void left by free-scoring Johnny Kenny, who left the Bit O’ Red for Celtic.
He has went on to score 11 goals in 20 League of Ireland appearances, and has netted twice in three European matches – including the delightful chip against the ‘Well.
An ex-Irish under-21 international, he also had loan spells with Queen’s Park and Dunfermline Athletic.
After a spell at Hartlepool United, the 23-year-old joined Falkirk and managed eight goals in 38 appearances.
Sligo Rovers boss John Russell said the strikers time in Scotland just ‘didn’t work out’.
"Aidan is really enjoying his football here,” he said when speaking to BBC Scotland after the match. “He is a terrific talent and certain places just don’t work out for players.
"The style of play, manager, that all comes into it.
"We’ve tied him down to a long-term contract and he is the leading goalscorer in our league.
"That's two goals in Europe for him too and this is the real stage for him in my eyes.”
Keena was well liked by the Bairns support – but was allowed to leave to return to his homeland after then head coach Martin Rennie brought in a new-look attack of Jaze Kabia, Anton Dowds and Leigh Griffiths.