You have to have a leak somewhere I am sorry to say. I live in NE OH, so same side as the state as you, and 2022 was a dry summer here. Our 1 acre pond dropped about 10", and I pumped water out of it to water my lawn. By mid November we were full again, and have stayed full since. I remember when my contractor dug my pond he hit shale which was oozing water up at a fairly fast rate. I thought that was a good thing, but he said if water can come in that way, it can also leave that way too. He covered it up with clay. I read that you hit sandstone, so maybe your contractor didn't cover it up good enough? Here in OH our problem is too much water. I think that this was only the second or third year in the 25 years of the life of my pond that the emergency spillway wasn't used. Your pond should have filled in less than a year. Ours filled in four months, and that was just from rain and snow. I have never pumped water into it, generally I pump tens of thousands of gallons out of it ever year. Maybe try some fluorescent green dye in your pond and look to see where it comes out from. If you don't see any, then it has to be going out through sandstone fissures. I wish you the best.
