Bots replace afk'ers?

Ok, so people might be pulling my leg or this is a legit thing. I just finished a game where my Syndra 'afk'ed' in the middle of the game. My Twitch and I were trying to push objectives but my entire team was never on the same page as me. My Poppy stayed farming at top and was never with us and always at fountain buying items or something. Our Elise was farming jungle and only participated in the slight skirmishes in the jungle and would always be killed in a 1v3. Basically it felt like a 2v5 most of the time. So, around 40 minutes or so (yeah long game we were behind because people kept getting caught out) Twitch and I destroyed their inhib turret and inhibitor and their first nexus tower (killed Lucian and Tryndamere). The rest of the enemy team respawned and killed us. I noticed how Poppy, Elise, and Syndra were at base in front of our mid inhib. I asked "Why is no one pushing with us? Where are you guys?" Poppy told me Syndra was afk and had become a bot. It was strange because normally afk'ers just go back to spawn. Syndra was just walking around the mid inhib and going places aimlessly like top lane. That is really strange. This is the first time I see this happen and I just want to know if people actually become bots when they afk.