This tutorial shows how to have your virtual content have a pop up arrival when it appears, rather than just "showing up". It involves minor scripting, use of Vuforia's "Target Default Observer Event Handler", Animations and Animator States. If you are trying to do this on your own, it can be very confusing as Vuforia has changed their code to call these function many times over the last few years.
Using Unity 2021.3.5f1 and Vuforia 10.12.3 to create Image Target Recognition Augmented Reality.
This tutorial is entirely on the computer and uses a webcam, no device needed, but my other tutorials show how to push this application to an iOS device.