According to the rules you play this game in 2 phases. The cards you play are used in the Delver Phase. The player aid is quite clear how it is done. Then you go to the Excavation Phase which I believe is what you mean when you write "pool die roll". Those are separate things and don't affect each other. Also note that when playing Lost in the Ruins you can reroll any one die. It doesn't have to be your own. If you would lose your Excavation Phase when playing this card it would make it very difficult to use to your opponents dice.