Forgot to take turkey breast out of the freezer until this morning

I have done this a few times, warm slowly and it will be fine.

and I'd take it out of the bag.

Hi there! When the breast feels fully pliable/flexible it's defrosted—when you press into the breast it should feel soft and you shouldn't come up anything solid parts (unless you're talking bone). Change the water out frequently while you defrost—once it gets really, really chilly, replace with new cold water.