Barnard converted from the spot to claim his 14th goal of the season and leave Ince fuming
"To lose to a goal like that right at the end is just devastating," said the Dons boss.
"It wasn't a penalty and referees continue to get the big decisions wrong. You saw it with Ireland in the week and refs are costing teams and countries too.
"I asked the ref at the end if he could tell me who gave it away and he couldn't, which seems strange to me."