Scent Discrimination Retry

I noticed something interesting with Wyatt last week. We were practicing scent discrimination. Wyatt picked up the incorrect article. He came about 1/2 way back to me, then decided to go back and get the correct article. I could swear that I did not move or utter a sound. Did I somehow cue him that he had the wrong article? Or did he change his mind and decide to go back on his own? In either case, I am amazed...