When I was 19 my mom pressured me to give up my daughter for adoption and allow her to adopt. After months of pressure she finally convinced me I would be doing the right thing. I signed the papers but at the last moment before the adoption was finalized she backed out due to her wanting to divorce my step father.(they did not divorce at that time)
When my daughter turned 3 I asked my mother to help me with babysitting because I needed to find a full time job so I could afford child care,and I wanted to move out of my sisters house.
Long story short she filed a petition for adoption (after she finally divorced my step father) stating I had abandoned my daughter.

I did not abandon her and I have documentation and proof of my contact and visitation numerous times to my mothers house for weekends etc.
My question is what to do next. She told me this entire time that she had used the old adoption papers and that there's nothing I can do about that. Having found out she actually did this abandonment petition, I need to know what to do to get my daughter back. My mother is now denying me visitation and phone calls.

If your daughter was adopted LEGALLY by your mother she is your mother's daughter now and you have no legal standing.

I'm sorry but that's how adoption works.

You can always argue that you did not receive notification of the adoption but, quite frankly, unless you can pay some hefty legal fees and take the chance you will not win, I would not even try.