The striker, who also had stints at Celtic, St Johnstone and most recently, York City, got on the scoresheet in a 3-1 victory over Salvesen.
Riordan bagged the second goal for St Bernards with a strike into the top corner.
According to a post on St Bernard’s Facebook page, a number of key players were missing from their normal selection.
It remains to be seen whether Riordan will feature in their next Champions cup game in Shotts.
Click here to see Riordan’s excellent strike - it starts at 42 seconds in.