The Glicko rating system can be brutish to newcomers, but this is the first I've heard of it reducing your rating after a win. You're probably aware that you have 3 live ratings, right? Sometimes that trips folks up; otherwise it's probably just a bug. Any of these threads will explain how the rating works if you're interested.
https://www.chess.com/forum/search?keyword=glicko+rd
How is this even possible? My initial guess is that it a bug of the phone app yet to be honest I am not sure how the rating works.