My Varus Unit Became An Enemy

Forgot to take a screenshot, but this is what happened.

I had a full bench, was around level 4, and bought a Lucian and a Varus the previous round. I was gonna sell my Lucian but accidentally placed the Lucian on top of the Varus. The Lucian disappeared, and then the Varus became red. I couldn't sell him when I tried to drag him down and clogged my bench the rest of the game. I could still move him around on my bench, don't know if I could upgrade him because I didn't try. If I placed him on the field, he didn't count as one of my units, so I could put another champion on the field, but when the round started, the Varus was considered an enemy, and my team killed him. When he respawned, he was still red, unsellable, and I couldn't do anything about him. If it matters, my Varus was on the farther right position of the bench, and the Lucian on the second to the right.