She took the tip back

Yesterday I delivered to a customer who met me on her porch when I pulled up. She told me it was her first time using the app and that she appreciated me delivering to her as her husband had recently had surgery and on top of that her car was hit in an accident. She told me to add a $20 tip to the order. I told her she needed to do that through the app but that the app already said she had tipped me $22. I told her that I appreciated the tip as this is my part-time job. She thanked me again for delivering and I left. I check back later and she took that $22 tip back and left me with $0. My first time being tip-bated and I am pissed.