The Church of Jesus Christ of Latter-day Saints

Birth was 1945, death was 2019. How do I find anything conclusive on this?

If someone was supposedly baptized but I can’t find a baptismal record, does that mean they may have been excommunicated (I know that’s old term, sorry)? The individual’s life is such that they may have been excommunicated, but no one in the family knows. Should we do their baptismal work or nah?