I can’t tell you why but it seems like plasma crashed (-> screen black and all opened programs gone) and restarted (-> came back). That’s what I can tell from your description. In your logs you can look for errors from plasma, kwin and maybe something with the gpu driver.

In theory, you could make a XMPP bot that can do all these things. Status information and executing simple commands shouldn’t be that hard but interactive commands might need a custom wrapper.