Just had an "Ah ha!" moment with the shot above. The back of the couch where the cat is sleeping is at an angle to me. I focused on his head between his ears and then recomposed to get him in the frame better. Even though the camera's focus was locked, the plane of focus shifted slightly when I recomposed because of the angle. You can see the pattern on the couch is sharply in focus while his head is slightly OOF.
I'll have to re-think focus and recompose when shooting at an angle like that. This may have been a case where having all the focus points available and the choosing the proper one would have worked better than focus and recompose.