It is Blue Eyed Mary - Collinsia verna. It's an annual and if it is disturbed in the spring before it has a chance to set seed, then it disappears.
Notice the two white petals up and the two blue below. Now notice the leaves. They are opposite each other on the stem and completely surround it with the broad bases. That tells you that this is Collinsia verna and not another Collinsia. [There are some all blue ones on the west coast.]
It's a short plant, around a foot or so high here. The blossoms are in loose whorls around the stem.
So pretty!
Here's more info on it from the Missouri Botanical Garden. And even more from Illinois Wildflowers.
