I've increasingly noticed people online using the following construction, sans "if": 

> Imagine you died on Spotify Wrapped day.

To my ear, it *feels* like the sentence should read:

> "Imagine **if** you died on Spotify Wrapped day."

I know that this is related to the subjunctive mood, but is the first construction correct as well? Or is the "if" necessary? Or is "imagine if" a colloquialism to begin with?

I've tried to research this topic but mostly find results on "imagine" used in the imperative sense.