Thank you for your reply! Yes, I have printed out the marriage registration from the OPR. Took me ages to find out the info. I found it by working back from James, my GG Grandfather.
Additional info.: Robert Sr. married Charlotte Ferguson on Oct. 25, 1835 in Camlachie. She was 24 years old! I believe, they had 3 children together. So, Sarah (obviously) died some time before that. I'm unable to locate a death registration for her, though. Robert Sr. was 60 in the 1841 (the first) census.
Thank you for your interest and for your time!