You'll recall that my first guess was an American flag.

Yesterday morning.
Yesterday morning.

Seriously, it looks like a flag, right?

From another angle, also yesterday morning.
From another angle.

Then, last night, upon leaving the office...

Okay, fine, maybe its not a flag.
Okay, maybe it's not a flag.

And then this morning on the walk to work:

The plot thickens.
The plot thickens!