All about Signals in Godot! 

It does appear this is the case, however, there's always an explanation. I've had dozens of different situations where I was able to hunt down a reason for it happening. It's still advantageous to do things in code when you are prototyping, because the most common ways to have signal connection issues is when you are moving things around in the scene tree after connecting them, or making a lot of changes at once without testing, or adding a scene to another scene, making it local and adjusting things in its subtree. Most of my issues have been with custom signals as defined in a script becoming disconnected. This one happens very easily. If your scene gets saved somehow with an error in a script that contains the signal...suddenly all those connections can be completely gone. Similarly, if you are using the @tool annotation, you can be in the middle of an edit to the script and pause too long...If you have something happening in _process or _physics_process or _input etc... anything that you could accidentally trigger execution in your tool script with, it can recognize your script has an "error" in it and fail to compile, resulting in any signals you connected in the node tab simply being gone. When you fix that error, the signal is back, but the connections will still be gone. So, to sum up folks: Do what @scotmcpherson is suggesting to avoid all these pitfalls and more happening to you and making your life suck.

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Same reaction 😅