If a blackjack dealer thinks someone was signaling to "hit"......but they really meant to "stay"....?

depends but if you are given a card you must play it you can call the manager and see what they are willing to do. most places have very explicit rules on how to signal and the dealer will ask if it is unclear. so if the dealer thought you were clearly signaling for another card than any review with the camera should back that up. unless the dealer is completely incompetent but that rarely is the case