This semester, my professor asked me if I could come in on a Saturday if I wasn't busy, but that she under stood if I couldn't. I said that if she let me know what time most of the students were planning to come in then I might be able to help out. She sent me an email the next day telling me that most students would be there from 10 to 12. I did not respond, and when Saturday rolled around, I decided not to go into the lab. A few days later I received an email explaining how my professor did not go into lab due to an emergency, but that she was grateful for all that I did to help students keep moving. She apparently assumed that I was coming in on Saturday.
The problem here was just a lack of clarity and explicitness. She should have asked for a more definite response, and I should have been willing to give one instead of ignoring it and making assumptions. There were not very big ramifications. I don't know if I could have accessed the lab for the students anyways, but even so, I think they were fine. I'm sure it would have been better had I been there, but next time I will just have to make sure things are clarified.