I was unable to find a variant with a 9x9 board that included this piece, but that doesn't mean such a variant doesn't exist.
Perhaps you slightly misremembered the powers of the piece. Modern Chess was invented in 1968 by Gabriel Vicente Maura, according to Wikipedia. It has a 9x9 board and features a piece called the "prime minister" which combines the powers of the bishop and knight. Unlike any piece in normal chess, it is capable of delivering checkmate without the help of another piece, if the opponent's king is in the corner.
It's also possible you may be thinking of Chancellor Chess. This was invented by Benjamin R. Foster in 1887, according to Wikipedia. It has a 9x9 board and features a piece called the "chancellor", which combines the powers of a rook and knight.
If you're sure that the piece was actually a queen and knight combined (and not a bishop and knight or rook and knight), then Wikipedia says this is called the "amazon", and that it has also been called "angel, ayanu, commander, crown prince, elephant, empress, general, giraffe, grand chancellor, maharajah, rettah, royal guard, superqueen, tetra queen, and wyvern".