Did I miss it?

So, I left Joey laying on this mat to play while I went to the bathroom. (He was parallel to the toy.) When I came back this was where he was.

My first thought? Did he roll over and I missed it? He's being trying more and more, and able to roll his legs over but always gets his arms stuck.

Joe and I talked about it later and figured it was just his scooting whilst trying to roll.