No mate ,your bait was eaten by mice ,voles or shrews .You will know when a mink or otter trys to drag bait out the back ,believe me .Just to add ,I was told many years ago that the best deterant for a mink was an otter as they wont tolerate them in the same territory.If theres no sign ,tracks of them Lloyd then rest assured ,you do not have mink on that lake .