Hello and thank you for entrusting me to assist you. My name is ***** ***** I will do everything I can to answer your question.
Legally speaking there unfortunately isn't much you can do. Employment in the state of CA is "at will" absent an express agreement to the contrary, meaning it can be terminated for any reason not amounting to discrimination on the basis of a legally protected trait (race, religion, gender, etc.) or retaliation for engaging in certain forms of legally protected conduct (filing a wage claim, taking FMLA leave, etc.). It doesn't matter whether the basis for termination is fair, reasonable or even true. So, since you could simply be fired with no discipline or write-ups at all, discipline and write-ups aren't regulated.
All of the above noted, it is expensive to re-hire and re-train new employees, and if you were to be fired, you could generally file for unemployment which would affect your employer's unemployment insurance premium. This is to say that employers generally do not want to terminate employees any more than employees want to be fired, and so employers tend to be rationale in these situations.
For these reasons, the best course of action in the circumstance you describe is to respond to the written warning with a sincere apology and an explanation for the mistake, if there is one that might help mitigate what happened. It sounds a bit harsh, but the only real job protection is to make your employer WANT to continue employing you. This, unfortunately, requires winning them over from time to time and using persuasion to demonstrate the value you provide to the company.
I hope that you find this information helpful. Please do not hesitate to let me know if you have any questions or concerns regarding the above and I will be more than happy to assist you further.
If you do not require any further assistance, please be so kind as to provide a positive rating of my service so that I may receive credit for assisting you. Very best wishes moving forward.
* Disclaimer *
Just Answer is a venue for informational and educational purposes only. No attorney-client relationship is formed by these communications.