I have seen the Foveran parish register on microfilm, and it appears they were married there:
Marriages
1826
August 20 James Findlay Newmachar and Margaret Ruxton were married.
Why the marriage was also recorded a week later at Newmachar I can't say, but I have seen this more than once in Scotland, i.e. a marriage recorded at both the bride's and the groom's parish, so perhaps it was a custom to in some way celebrate the marriage a second time at the groom's parish.
Peter
PS Another bit of (circumstantial) evidence re the parents of my James Findlay. Anne Findlay, born 1800 at Upper Rannieshill, i.e. a sister of your Robert, married Robert Connon of Udny. Their son Thomas Connon, born 14 Sep 1832 at Udny, came in 1853 to the same village (Elora) in Ontario where my James Findlay and his family had settled in 1836. A son of this Thomas Connon, John Robert Connon, wrote a book about the history of Elora and in it mentions the family of James Findlay in quite a bit of detail, as if (so I hope!) he was related:
The Early History of Elora and Vicinity, by John Connon, p.92:
About this time a young man came on the scene who was to play a conspicuous part in the community. This was Mr. George Barron, whose native place was Savoch i'Deer in Aberdeenshire, Coming to Canada, several years before this, he had worked in the vicinity of Whitby. There he heard of the Bon accord colony, and came up to investigate. He returned some time later, and, about Christmas, 1835, married Miss Elspet Watt, who had, up to this time, kept house for her brother. This was the first marriage in the settlement. A few days later. Mr. Watt set out on a visit to Scotland, leaving the newly-married couple to look after his house until his return. Having married in Scotland, Mr. Watt again sailed from Aberdeen on the 16th of April, on the ship 'Pacific, and arrived at Elora on the 10th of June, 1836. In this, the fifth party there was, besides Mr. and Mrs. Watt, James Findlay, who was born in the Parish of New Machar Oct 5th, 1804, and his wife, Margaret Ruxton, from the Parish of Foveran. Their four eldest children were born in Scotland, their family being : Agnes, Mrs. George Smith, living in Brantford ; William is the well known auctioneer and resident of Salem ; John is in Victoria, B. C. ; David, lived for many years in Salem, died in Windsor ; James is in Shoal Lake, Manitoba ; Alexander died in Toronto ; Robert is in Sudbury, and Charles in Shoal Lake Manitoba.
("Agnes, Mrs George Smith" is my great grandmother)