Stock received his first booking following an altercation between Clarets defender Michael Duff and Reds striker Marlon Harwood, and the former Barnsley man received his marching orders for a 37th-minute foul on Jim O'Brien.
Sean Dyche's side performed creditably with 10 men but went down to a strike from Barnsley substitute Danny Rose in the 85th minute.
Stock told the Lancashire Telegraph: "The first yellow card I think the referee's booked me by mistake. I don't know what he was seeing, and it wasn't just me. Fair play to players like Marlon Harewood who was trying to tell the referee he was booking the wrong person.
"The referee didn't give me a reason as to what he booked me for, he just said 'I've seen it' and he said it numerous times. He never actually said I'd done anything, which was a bit confusing.
"We've seen it back on the replay - I got pushed in the back and then hit in the back of the head. It was a double whammy really, and to my surprise I got booked for it."
He added: "Maybe I should have probably done better in not getting booked for the second one. It's not often I get sent off and I've never been sent off for two yellow cards so cheaply."