There is one awful possiblility that comes to mind. The cholera epidemic of 1849 that killed many, many people in Sandusky. Looks like their last child was born there in 1848 so if you can't find any of this family after 1850 it is a logical explanation. This epidemic lasted a few years. There is even a mass grave where many Sandusky victims were buried. Google "epidemics in Sandusky OH"