Welcome, and I like your handle.

I've never seen that, either. What is standard practice is to give that card to the dealer. If the dealer didn't need a card (not the case here), then it would be burned before dealing it to first base in the next round. They can't back up a card, but they certainly should have played it forward for the dealer.

And no, the dealer shouldn't have hit the 18. that violates the rules of the game.