Was it ever there though? Or you mean the Google app?
Is ASSISTANT (Not Google) still in your app drawer? I don't have it in mine, and don't recall ever having it as a standalone app. The Google app, however, should still be available both on the drawer and on the side key shortcuts.
Which variant you have the US or international?Yes, Assistant app is still available as a separate app from the Google app. They both are in my current app drawer and works differently. Similarly, prior to the upgrade to One UI 2.0, the Bixby button remap list of available apps to assign included all apps from the app drawer but now is excluding the Assistant app.