I might have found the long-looked-for parents of Jakob JOST (oo 1816 Marianna LAGARD; +1849 Sigmundfeld).  They are Christian and Margaretha JOST and I found a couple of their children christened in Lowrin between 1787 and 1795. They had two sons named Jakob/Jacobus: one born 1790 and died 1794, the other born January 1795.  This Christian JOST *might* be the same person as the one passed through Vienna in 1784 and I wonder if anyone has any more information on him.  Many thanks!