Talking about ones boss on an email chain to a colleague via reply rather than reply all.
Colleague gives an update on events and adds in previous respondents without reading disparaging email.
Email retraction is attempted after heated phone call. However, retraction is only possible if email has not been read.
Email has been read by boss.
oh the pain, the pain of it all.
I wouldn't worry about this too much. It happens all the time in the modern work environment. And keep in mind that it is assumed in most organizations that everyone hates everyone above them in the food chain and is angling for their job. Thus, your hate for your boss comes as no surprise to him. The only exposure to you is that he can now hold this over your head and if he really wants to squash you, and you have no leverage to successfully counter his move, you may be looking for a new job.