I'm sorry this has happened to you - Most employer's I have worked for could really care less about your child care arrangements. They see that as your problem not theirs. I happen to have a flexible workload that can be handled by phone and fax with emergencies runs to seperate facilities so it's not so much of a concern to me as it was in the past. My current employer is so laid back and family oriented he almost bends over backward with these situations.
That being said - You have to firm up your child care arrangements so this kind of thing doesn't happen again. How old are your kids? If the oldest is 12 or older they can legally supervise their siblings. Otherwise do you have a trusted friend or neighbor you can call on in an emergency. I always try to have at least two babysitters on deck for that purpose.
Looking at it from the employer's point of view - you have to understand thay have a business to run and if they got slammed on the day before Thankgiving which is entirely possible they would have a big problem on their hands. It may have been better if you could have worked the morning and left early than take the whole day off. They may also wonder if this is going to happen frequently on such short notice.
If I were you I would call them and see if you could meet with them personally - perhaps even to pick up your last check and talk to them without being angry or upset. Tell them that this situation was quite unusual for you and you understand what a bind it put them in. Tell them what measures you have in place to prevent this in the future and see if they can give you another chance. If as you say the job was working out well otherwise they may agree.
Hope everything works out for you
Hppy