Apparently not. His name does not appear (either as 'Rumford' or 'Thompson') in the list of recorded discoveries in the link.
Count von Count was created in 1972.
Count of (Graf=Count, von=of)
Count Otto Von Bismarck
what year did L. Von Brady discover hydrogen
Count von Count debuted on Sesame Street on November 27, 1972
Ladislaus von Rabcewicz died in 1975.
Count Karl von Stürgkh was born in 1859.
Count Karl von Stürgkh died in 1916.
Count Heinrich von Bellegarde died in 1845.
Count Heinrich von Bellegarde was born in 1756.
Count Ludwig von Cobenzl was born in 1753.
Count Ludwig von Cobenzl died in 1809.