Since you're not reporting something large and heavy sitting there, I'm going to bet on a fungal issue. As to what, precisely, that's impossible to say without much closer and more expert inspection.

Poke around a bit. Do you see white or gray threads? (Wash your hands afterward and do not touch your grass or any other grasses until you do so).

Does your neighbor water, or have a watering system that automatically waters the lawn, or is your weather quite wet at the moment? Or is that a naturally damp area for some reason? Engineering controls would include cutting down the water--fungi don't like being dry, and optimal watering for most lawns is once a week, deeply.

Treatment, initially, if it is a fungus, would be any good off-the-shelf wide spectrum anti-fungal.

It's now far too late to reseed in Michigan, although your neighbor can wait until February or March, spread seed then, and allow it to sprout by itself when the weather warms. It's not optimal, and the area will require care through the summer and probably a reseeding again in fall, but snow seedings are the second-best (and not very good) way to get a lawn area started.

It looks like there was a kiddie pool or a sandbox structure sitting there for a while. Did the neighbors grass just start dying out for some reason, or was something sitting there at one time to kill off the spot?