Didn't Know About Unwritten Rule!

Dear Experts, Two days ago, I was at a team meeting and we were discussing a new client. The meeting ran on longer than it was planned for. I had an appointment after work, so I announced I had to leave. I immediately got a funny look from my boss and co-workers. The next day, everyone was acting annoyed with me. My boss wouldn't even look at me. Finally, I asked a co-worker what was up. I've only been at this job for about 2 months. She told me it's an unwritten rule that you stay for the duration of a new client meeting because the manager believes they are so vital to the successful kick-off of the project. I had never heard of that from my boss and kinda got mad at first. But now I'm worried. Should I apologize to my boss? At the same time, shouldn't it be made clear if there is a policy like that? How do I fix this? Here is how our CAREEREALISM-Approved Experts answered this question on Twitter:Q#360 This job has most likely been filled by someone else. Just move on, it isn't worth the trouble any longer. (@gradversity) Q#360 Explain that u were unaware - won't happen again. Business rules dictate fulfilling meetings etc. to conclusion. (@DebraWheatman) Q#360 Agree U should apologize. Many actions that demonstrate U R behind company goals R unwritten rules=judgment calls. (@resumeservice) Q#360 Apologize, will stay for whole client mtgs; re U, assume all late aft mtgs run late, dont sked appts. (@juliaerickson) Q#360 Have a 1-on-1 with your boss and apologize for the error in protocol. In the future, book time off for appointments. (@gradversity) Q#360 It's unwritten. No way for U 2 have known. Apologize & recommend that new ppl get the hint ahead of time. (@beneubanks) Q#360 Let boss know U meant no disrespect. And ask about other preferences. Communication vital. Demonstrate desire to improve. (@dawnbugni) Q#360 You should apologize & promise it won't happen again. Doesn't need saying to attend whole meeting. (@heatherhuhman) Our Twitter Advice Project (T.A.P.) is no longer an active campaign. To find an answer to the above question, please use the "Search" box in the right-hand column of this website.