St. John's Cemetery in St. Bernard was founded in 1849. It is connected with St. Mary's Cemetery in St. Bernard. I have ancestors buried in St. John's, but they do not show up on the St. Mary/St. John site. Apparently the lot was purchased by anothe person (whose name I do not recognise) and it is only by luck that I found my family a number of years ago.
Perhaps your ancestor was buried there. You might have to speak with an individual in the office, or write a letter.