[Gameplay] Seeing enemy pings

Recently (in the last week) I have noticed in a few of my games that there are random "on the way" pings that show up on the map. When I look to see who pinged in the chat, however, there isn't a log/entry of the ping. Then I notice that an enemy shows up near the area of said ping. At first I thought there was no correlation, until last game enemy blitz roamed mid multiple times. Each time right before he showed up there would be an "on the way" ping that didn't say who pinged in chat. I also know it wasn't my team that sent it. I was the jungler and my friends with which i was skyping were bot. None of us sent it. Neither mid nor top made a movement toward the ping, which was located just under mid lane.