Adobe Lightroom Mobile product updates are released.The December release updates contain a fix for this issue.
Updates will be available via the Apple App Store. Note that it can take several days for some customers to receive a notification of an available update via their App Store.
Did you recently change device languages? I was able to reproduce a problem AI Remove becomes hidden after changing my device language (from English to Japanese). Quitting the app and launching it again showed AI Remove again.