That's weird. First you need to discover what killed your plants. That sounds an awful lot like how quickly vine borers can kill a plant. Healthy one day and dead the next.
Do you have cutworms there? They can also kill a plant quickly by cutting the root and separating it from the above ground plant. I think they are probably more of a problem on young plants?
Your problem doesn't sound like a disease. Diseases make the plant look sickly for a time before it dies.
I like what you said about harvesting by cutting the stem with your knife. That is how I do it too. Not so much to protect the plant, but to keep the squash looking good. You can scratch them up badly when picking because they are so tender, and sometimes the squash itself breaks instead of the stem if you just twist it off. Yes, I have broken or pulled plants before trying to harvest the fruit. It happens.
I have only seen vine borers a couple of times. Most years they don't make it here. They cannot winter here because of our harsh winters and must move in from warmer climates, but the times I have had them they caught me off guard and about wiped out my squash.
My zucchini put on quite a bit of squash, then took a vacation. They are blooming again and I expect they will produce more. My squash usually all make it till frost, when they quit immediately. If they didn't grow till frost, I Would be looking for a reason.