You got disconnected.
https://www.chess.com/blog/News/how-to-adjust-your-live-chess-connection
https://support.chess.com/customer/en/portal/articles/1444918-my-internet-connection-is-fine---why-am-i-getting-disconnects-
Clients on the site don't connect directly and your opponent can't cause issues with your connection since they have no way to find your connection details.
Now I could be two possible conditions. 1. Chess has a glitch that needs to be fixed or 2. Somebody intalleda program to cheat. Should be investigated. I have seen this in yahoo. Tht is why I do not play in that forum.