Lesson Learned?

My oldest decided that he wanted to make some money the other day. He looked at the various jobs I've posted and decided to vacuum out our van. Next to the job I've written an amount and on this particular job I pay $5 which is more than any other job because its the most difficult. I had to help him get the shop vac out and to the sidewalk but he hooked the extension cord and everything else up himself. He worked at if for an hour or so and I checked his work. I had to point out a few spots but was very surprised at how well he had done. Anyway he got the $5 and started talking right away about how he was going to spend it. The next day we went to the grocery store and while I was putting my baby in the cart he slipped the $5 into one of those claw machines that are filled with stuffed animals. When I turned around I was so upset because Jeff and I have told him a couple of times what a waste of money those machines are. He got three chances and surprise..... he didn't get the toy he was trying for. Not only that... the machine took his 5 bucks, didn't give him more chances, and didn't spit any change out. I made him talk to one of the clerks and she informed us that the store didn't have a key because the machine was owned by a separate vendor and if we wanted our change we had to call some number that was posted on the machine. I had all four kids with me and my patience was running thin, all I wanted to do was go home and not bother with it. Mr D was not very happy and I could tell he felt really bad. I hope he learned something. We talked about the reason those machines do what they do and what their purpose is. I'm not sure I dealt with the situation the best way, I'm starting to wonder if we should have tried harder to get his change back. As a parent I get so frustrated at times like these because I need to teach but at the same time stress and irritation take over and I don't feel like my children are learning the lesson when I can't pull myself together and face the situation in a better way. I want so bad to be a constant in my children's lives but often feel like a hypocrite because I myself tend not to handle stressful situations in a positive way.