Should I tear my laywer a new one?

So last year my parents' number came through and they filed for i-485 - the rub being that I couldn't get on the petition with them bc I had turned 21 that year. Now I find out that a person in the same situation as me, who had been 21 for quite a few months when his parents filed for i-485 got on the petition anyway, and now he got his green card. I thought this wasn't allowed? I'm seriously mad at our lawyer. ARGHHHHHH

Have you heard of the Child Status Protection Act (CSPA)? Most likely your friend through that was able to subtract several months from his age making him under 21. The time it took to process your application which could be months or years depending on individual. Though you cannot subtract the time it took for Priority Date to become current after initial approval of petition.

I did, but I thought that only applied when you were close to turning 21 on the date the petition was filed. Both of us were 7 to 8 months into being 21 when our respective parents filed for i-485

As long as you were under 21 when original petition (I-130) was filed you could potentially benefit for CSPA.
http://www.dhs.gov/files/programs/ci...econ-cspa.shtm

you have one year to file for child protection act is my understanding. get on top of it.

yes you need to prove you 'sought to acquire' within a year. I believe there's been a recent decision on what that meant in the courts, but I'm not sure.