What are the options if an iPad is purchased after you watch the previous owner sign out and reset device yet when you get home with said device and try to sign in it is activation locked even though you oversaw the prevention of said lock?

Lady was selling an iPad 2. I met with her to purchase the iPad 2. Before purchase was finalized I watched her sign out of her account then reset the device. Also before we traded money for device I played around on the iPad for a few minutes. As I had not technically purchased the device yet I did not sign into my own account on the device while I was playing around. Once I checked through the settings and also turned the device off and on a couple times making sure her account was completely removed we completed the buy. I was running behind for some other appointments I had after purchasing the iPad so setting up my apple id right away was put off for a couple hours until I got home. Once I was home I set out to set up my new iPad, I powered it on and was very confused to find that it is now activation locked, and as it does not show the complete email of the id it is locked to, only the first letter this letter and the remaining shown characters match the previous owners information. I tried contacting said owner and the number I had been contacting her with was since disconnected and the email address where initial contact was made kicks everything back to me saying I have an invalid address and the message can not be sent.