Teenager blues

My 15 year old asked me to find her biological dad a week ago.

A little background on him... we met in our early 20s, in a relationship for 4 years. It was a toxic relationship he was super insecure and a coward while I was stupid and a hopeless romantic after our breakup he disappeared. He contacted one time volunteering to take her to daycare for me he did that for two days on the last day as he was dropping her off he asked if I could take him off child support I kindly said no haven't heard from him since she was 4. I've stayed in contact with his aunt we speak every now and then but she knows everything about my daughter. He could find her if he wanted to.

Out of curiosity I checked social media, google I even had a relative of mine check the military... nothing. I found him on Venmo but he hasn't made a purchase since 2016.

I tried explaining this to my daughter as politely as I could but she's hellbent on finding him. My husband has been here since she was 5 he supports and encourages her to find him. I just don't understand this new obsession to find him. I'm still going to help her even tho I know for a fact he doesn't want to be found. I want advice moving forward on how to handle this situation.