How did he do that?

Graham turned 3 weeks old yesterday. He is getting much stronger and can really pick his head up high during tummy time. He is eating A LOT and growing fast! Last night when he started signaling for a bottle I found him scooted down toward the bottom of his bassinet. I thought "Surely I put him in the middle like always. Was I that sleepy when I put him down?" Then I went downstairs to get a bottle and when I came back, I found him like this...totally turned sideways. He's moving around somehow!