There's a very confused pause as the bird collapses. Considering his familiar has so far remained unmurdered, Cole also didn't know that could happen. So he stares for a moment at the collapsed phoenix before that shrill voice starts up again. "What are you waiting for?! Go, go, go!"

Oh, right, he needs to leave. Taako finishes casting Magic Missile as Cole starts to book it, running away from Taako as quickly as he can, concentrating so hard on remaining unseen. You can't see me, you can't see me, you can't see me.

It works. He's still detectable either via magic or weird elf senses. But visually? Cole just isn't there anymore. And physically, Cole is just running the fuck away, trying his hardest to just get out of Taako's range and hope that the elf decides to ignore him.