Blizzard HAS been improving the situation. As a player since the closed beta time, 6 years ago, I have seen some improvements for sure. For example, the game will often detect when you are disconnected, and you would then see a message that it is attempting to reconnect, and then once successful, you can continue the game. Once that game is over, it asks you to quit Hearthstone to restart it and thus fully reconnect.
Also, if you find that you are disconnected, you can force-quit Hearthstone (Alt+F4 in Windows) and start it again as soon as possible, in which case it will log you back into the game in progress. I am assuming there are other ways they have improved behind the scene. But given the number of variables between your computer and Blizzard’s servers, the connection could be lost along the way, without you or Blizzard being to blame.
I also play a fair amount of Rocket League, and it does happen, once in a while, that a player stops moving, then disappears completely with a “connection lost” system message in the chat. Connections issues do happen. If they happen to you, specifically, a lot, then chances are the issue is closer to you. Either your home network, or your ISP’s network. I am not a network expert, but the Technical Support forum has some of those lurking around, they can help you out. However, if it was just the one time, then don’t worry about finding the cause.
Remember that turns last only 75s (I think… or is is 80?), so if your opponent’s turn is taking longer than that while they don’t do anything (or just keep hold of a card above the field), you might have disconnected. If you opponent holds a card above the field AND emotes (or you can see the other cards highlight as they hover the mouse over the cards), then it is definitely a disconnect, since it is not possible to use the mouse to hold a card and emote at the same time! In that case, very quickly force-quit and restart to return to the game in progress. If you do it quickly enough, it will still be your turn.