Obviously none of us were there, but it seems very unlikely that they terminated a 22-year model employee for a single, undocumented bad result, especially when others have been given multiple chances. It sounds like there's going to be more to the story.
That's what zero tolerance looks like. Same stupidity that expels 8 year olds from school for bringing a toy soldier with a 'gun' for show&tell and imprisons people for 25 years on their 'third strike' even if the final offense was check fraud.