I have several times changed batteries in my H592 units only to realise later that I turned the top in the process and have set some crazy override temperature like 24C. Is there a way on the unit itself to a)tell you have set an override b)cancel it?

One of my units I locked the head to stop accidental overrides but I discovered this setting is lost when you replace the batteries, which is annoying.
Now I can't remember how to lock it, I've gone through all the settings and cannot see one for this. How do I lock (and unlock) an HR92?