Im a smaller based LL (I also dont really like using the term landlord. Im basically management and maintenance). For larger complexes they use outsourced property management companies to handle office stuff and everything is usually auto generated from a system. So some person in a chair gets an alert your late and then a notice is stamped and put in the mail. A notice means dick and wont affect anything.

As for not telling you its going to be their word against yours. They will say a letter went out, or some email etc etc. You will say you never got it. If you have a good standing with the place they will usually let it slide and waive the late fees and the notice just goes away if they dont start proceedings. A notice has really nothing to do with the court system until after the 30 days and the building goes and files official paperwork. Each state may differ a bit though. The notice to vacate was probably already being processed by someone else while you were talking to your person.

tenants have to protect themselves and remember so do landlords. The courts are NOT usually on the LLs side even if they are good ones. We have to be sure all paper work is filed promptly and correctly or we can be stuck with an awful tenant because the courts decide to make our lives hell. its not a personal thing, remember for every good landlord there are 10 bad ones, for every good tenants there are a hundred bad ones. the odds are just stacked against us so we have to be super on top of everything.