Don’t assume because that ancestor disappears from the records that he was dead. It’s also possible that he simply pulled up stakes and left the area and his family.
It is possible that there may be a reference to his disappearance in the local newspaper. It’s also possible that the family knew the person willingly left their family and did not want to draw attention to it. The person may be mentioned in court records or potentially a probate file for a deceased relative of whom they were an heir-at-law. If the disappearing ancestor had real property find out how that title was transferred to the subsequent owners.
Depending upon the time period and the location there may be no record of what happened to the person.
Sometimes a disappearance from the records means a person is dead. Sometimes it means they had moved on to a new location and a new life.