"Pioneers of the Old Monocacy" by Grace L. Tracey and John P. Dern, pages 46 & 229, shows Bush Creek as on the southern edge of the New Market area and south of the town of New Market. The Monocacy River flows south into the Potomac, running EAST of Frederick, and Bush Creek is a branch east of that, flowing west into Monocacy. The town of New Market is EAST of Frederick and today on I-70.
It seems doubtful that a family residing in Allegany County would witness a marriage for a couple that resided east of Frederick. Of course, the records tend to indicate that the sons of Mark Brayfield did not move with him to Allegany County, and his purchase there was dated 2 months after the marriage of Johann Hegemann and Anna Aemelia Brafiel.
Neither Hagerstown nor Greene County, PA, are likely locations for this marriage which is recorded in the records of the Evangelical Church in Frederick, MD.