I may be wrong, but I'm guessing that you're not seeing the whole picture here. The other kid may have called him that late to whine about having to work seven days in a row even though he knew his schedule well in advance. Pehaps he was invited to do something, and he's using the seven days straight as an excuse to take off at the last minute. The boss was probably irritated, but agreed to ask someone to fill in. Notice that he didn't tell you that you had to work. He asked you, and he may have asked others. Because he was already irritated with the other kid, and he didn't consider this an emergency situation, he opted not to call and wake people up. He simply sent out a text on the off chance that you were awake and wanted some extra hours. I would have replied with a text saying that I already had plans, but thanks for the offer.
Attitudes like that are what worries me about retiring from the Army in a few years. I have an open door policy, and my Soldiers know that they can call me at anytime to talk about anything. I try to keep it at a minimum, but occasionally, I have to call one of them about something. It would be a very long day for them if they decided to cuss me for calling on their time. Civilian life is definately going to take some getting used to.