The striker featured as a sub 3 weeks ago against Kilmarnock but was kept on the bench at Falkirk the week after. He then had to swap his seat on the bench for a seat in the stand at Kilmarnock last weekend.
Yesterday's snub has angered Riordan who, despite a number of impressive performances, has failed to win a regular place in the Celtic first team.
Celtic rejected a £600,000 bid from Burnley for the 25-year-old during the transfer window as did not match their £1million valuation. An insider at Turf Moor said: "He clearly has no future at Celtic. They aren't even playing him, so how can they justify their valuation?"