Tbh cold butter isn't really why they spread, it's more about the dough being warm or your butter melting too fast in the oven. Cold butter straight from the fridge usually makes cookies thicker if anything, so something else might've been going on.

Oh man, yes, I did this too and it saved my butt more than once. I worked at a call center for two years and kept a little legal pad by my phone where I wrote down names, times, and the crazy stuff people said. This one dude called me a stupid cow and said he hoped my kids starved, so when he called back to complain about me I had the whole thing written down. My manager read it and told me I should have hung up on him way sooner. That notebook also helped me remember who promised what to who, because customers lie about that stuff all the time. It's not luck, it's just smart, because people act real different once they know someone wrote down their exact words.