It is interesting that a large part of what wikipedia says about this work is in fact coming from the liner notes on this recording. I suspect this is one of the few recordings around, and the liner notes have been written by someone that did a lot of studying into Haydn.
The title of this work is actually not correct. This is not a Mass for the patron saint of music. This is actually titled Missa Cellensis in honorem Beatissimae Virginis Mariae. So it is dedicated to the virgin Mary. The Cellensis refers to the pilgrimage church of Mariazell in Austria. Haydn went there on a pilgrimage himself.
Sources are unclear about dating this work. Currently communis opinio holds it was written in two distinct periods, but both earlier in Haydn’s life: 1766 and 1773. In 1957 the work was discovered between anonymous composers. Discovered, by none other than the aforementioned writer of the liner notes.
Although the sheets had Haydn’s name on them, at one point it was crossed out, for reasons unknown. Maybe by the same person that added the dedication to Saint Cecilia.