Yes, it is possible, even probable, that employees took "seconds" home. But they would have been marked with ERIE like all of the other pieces that were coming out of the foundry. The only way (see note below) an an ERIE skillet left the Griswold foundry without ERIE on it was if the pattern did not have ERIE on it. And I have never seen any evidence that this occurred.
Note - The only way to make an ERIE skillet that did not have ERIE cast onto the pan, and using Griswold's patterns, would be for the molder to obliterate the ERIE when finishing the mold. We know that molders had to touch up the green sand molds from time to time because there are special tools molders had at their disposal just for this task. So this would be the opportunity to remove the ERIE from the mold. This is certainly possible, but why? Even if this was what happened, I suspect that there would be some evidence in the casting of the molder's hand at work.