Probably the invasive Commelina communis.

The photo is so bad I am really only guessing mostly based on your description.

If the id is correct, the problem will be eliminating it...not ordering seeds on purpose..

The photo is bad, I am sorry. I would not want to eliminate it. My yard is full of spots where things won't grow, and the cats like to go. Namely a spot under my gum tree, and two shaded flower beds. This stuff grows on its own with no intervention.

yes, that is what it is and is says grows in disturbed soil- so when I planted my mint that must be what prompted it. reading about it on wikki- it doesn't have a very good reputation. why is it so hated?

Because it will take over every square inch of ground if you let it, and by using the words "let it" what I really mean is that you won't be able to stop it from growing even if you want to. The harder you try to remove it, the more it will grow. The more you hate it, the more it will grow. Most gardeners like to grow a variety of plants. Commelina would like to take over the world and be the only plant. So, if you like it and you don't think you'd mind having nothing but commelina, go ahead and encourage it but do so with the understanding that it wrote the book on invasiveness.