Oh gosh, I'm so sorry. Yes, you should have gone with your gut and hired a flooring company. Sanding as well as screening should not be done by amateurs and it sounds like that is what happened.
Now, first, you can't change the color or use a stain without sanding, so that may be problem #1. It is possible that a stain wasn't used and it was just a tinted poly. But, problem #2 is sanding marks. You shouldn't have those if you screened. Screening just takes off some of the poly. It sounds like he might have gone down to some of the wood.
I can't see it, but based on what you described with the marks and uneven sand, you will probably now need to do a full sand & refinish. And, that will take a lot longer than 2 days, esp when you consider the drying time.
This post may help you on the time frames, but even w/ water based poly, you still need to allow for the stain to dry and and after all the coats of poly at least 2 days before moving furniture (4 days w/ oil based)...and all of those are after the last coat of poly.
http://theflooringgirl.com/blog/refinis ... -take.htmlDebbie Gartner aka The Flooring Girl
Westchester County NY