I'm sorry you found out about their wood quality this way. You will not have any better luck at Lowe's. Home centers carry the lowest quality wood they can find to keep the price down. Their 4' x 8' sheets of plywood has lots of voids in them and at times as you found other undesireable debris. Support your local lumberyard. Will you pay a bit more? Most likely yes. Is it worth the difference? You bet it is. For smaller sizes than a quarter sheet (2' x 4') you might want to buy the baltic birch plywood from Rocklers or Woodcraft.