If a person is hit, will there necessarily be bruising seen? pt. reported being hit, but police found no evidence. not sure when event occurred.

Not always.: Whether bruising occurs depends on force behind blow and what was hit. Spanked children are certainly hit hard (unfortunately) and don't bruise. Slapped cheeks may not bruise either. So there may be no physical sign of the violence. It is still wrong, and it still causes damage (physical and emotional), even though there is no outward sign.