i worked at M&S whilst at college as a trolley & bag boy. in my spare time – of which i had lots – i’d go around with a red marker pen correcting the spelling and grammar on the staff notices.
i got a warnimg once from my manager because i had corrected her bosses notice and had been caught on camera.
each time her boss saw me after that i’d smirk at her.
The internet, helping stupid people advertise their stupidity to the entire world since 1994 (or thereabouts)
To give you a warning for correcting a senior person’s incorrect grammar is just immature and a sign of poor management and culture. Shame they didn’t thank you for improving the quality of their communications. On the other hand, was the warning for your own poor grammar? 😉