said by perplexed :I would insist that he sands down to bare wood and makes sure there is nothing left. Then come with fine sandpaper (first 80 then 150 grit). Only then will the floor be ready for poly...
Should I now insist he fine-sand the whole floor (two rooms and a hallway) again so the new coat will adhere, then use fresh satin stock?
Note that there *will* be imperfections after the first coat, but sanding again will take care of them. It should be almost perfect after 2nd coat, and 3rd coat should come out smooth.