I noticed that portraits I qualified for in the Tip shop and did not purchase are disappearing one..

They were temporarily removed to prevent a glitch in the game; they will return when the issue has been fixed . Here's the official statement: "Hey Detectives! Our team has identified a game issue in which special drinks could be unlocked by purchasing portraits from the Tip Shop. As such, we have temporarily removed the affected portraits from the store. Rest assured that our team is hard at work and is aiming to bring them back as soon as possible for you to unlock and use! Thank you for your patience!"