This is perhaps a case where simplicity is the best approach. These hidden object games are very simple to write. They're 2D and just a set of images that blend in with the background, requiring the gamer to find these special items. You do not need a game engine at all. Any UI library like Win32, MFC, WPF, wxWidgets, Qt, or gtk will suffice for writing a native based application. Alternatively, you could use Flash, Silverlight, or HTML5 if you want to write a web-based version. All of these APIs support key functionality that your game will require, such as displaying images and detecting when the mouse clicks on a specific graphic. If you wish to support sound or music, then the web technologies offer a straightforward API. If you were to go the native approach, then you will need to lookup XAudio (formally DirectSound) or OpenAL. Both have plenty of documentation and samples to work from. If there's anything more specific you would like to know, let me know.