My car has a boyfriend

Okay, here is my question of the day...

So can anyone please identify this bird for me?

We kept seeing down the road in the swamp near us from around March to mid-April and then it disappeared for a month. This morning it was in the neighbor's yard and waddled over to our yard when it saw my kids and I come outside to look at it (which makes me think it is domesticated.)

It let me take pictures for a while. And then, it saw its reflection in the car and it would not leave for the longest time. Kept squawking at the reflection, ruffling its feathers, and then gently pecking at the car. I had to go meet my husband at the garage, and then we ran errands at the same time. We've come back and its nowhere to be seen right now, though we did find its muddy duck/goose footprints up on the deck and the bag of dog food was all over the place. We'd bought a different food to try and it contains dried banana pieces, those were missing from the pile of food that dumped out.

We've been through our bird book and the closest we see for coloring is a snow goose, but the beak is really, really lumpy at the top, so snow goose no longer fits. We're puzzled to find out if anyone can identify it?