Man that sucks, the thing is that some people think that the work done on your car is good, or a the very least don't know any difference. Not saying that was the case but I've had people come to me in the past and say oh I just need someone to paint my car I've done all the prep work and its ready for paint. Most times I just tell them sorry I'm not what your looking for to do a paint job for you! It's way easier then crushing them by showing them everything that they did wrong and then they get very pissed off at me.
Now if they paid someone todo that same work for them I have know problem letting them know what was not done correctly in a nice way.
And then there are those that just flat out want to rip you off and those kind of people just suck
At this point take what you've learned and move forward. This is why I didn't want to buy my new car unless I know the person or I can go get it myself or at the very least have someone close by take a look for me.