The Reset Config resets ALL configuration to default so as Ralph said, it is probably in AP mode now. You can edit the config.txt on the SD card, removing the "#" in front of the wifi_ssid= and wifi_password= items to have them reconfigure the device again, or put a config.txt on any USB flash drive with just those two lines in it and HeaterMeter will copy into the active configuration when it boots the next time.
No there's no way to block it. I'm not sure what setting you're accessing so frequently that causes you to mistakenly activate the Reset Config option, but you can consider using the left button to go back rather than pressing the right button to cycle completely through the menus?
I'm actually working on the menu system currently to add some more stuff to it. I'll look at making it a double select option though so it you'd have to go to Reset Config? set it to Yes. Confirm by going to the next menu where it can prompt with an Are you sure? or something. Also maybe make it so the second screen prompts for what to reset like: Are you sure? "Cancel", "Yes", or "Full Reset". Don't hold your breath for that though!
That's not a change in the menus, that's a huge change to the Pi's systems. Also it wouldn't have helped because reset config wipes everything to a blank filesystem (which is the only way it can work reliably).