My mother's male first cousin is a direct maternal line descendant of Sarah, so I decided to test his mtDNA to see if I might get lucky and find something meaningful. Since mtDNA is not often helpful for genealogy, I know that this is a long shot.
Yesterday, I received the HRV1 results:
Haplogroup I
HVR1 differences from CRS:
16093C
16129A
16218T
16223T
16263C
16391A
16519C
I don't have any experience with mtDNA Haplogroup I, so I have been doing some research. According to Wikipedia, it is quite rare and found in low levels throughout Europe, the Middle East and South Asia. Reviewing the mtDNA I Haplogroup Project, I did not find any matches.
According to FTDNA, there is one exact match (HRV1). I contacted her and learned that she is also researching a Sarah (maiden name unknown) from the same area and time period as my Sarah. We both suspect that our Sarahs were of German ancestry, but have no documentation of their origins or parentage. Hopefully, this match will bear fruit in the future, but for now both genealogical brickwalls stand.
I am still waiting for the HRV2 results, but I don't expect to have any new matches at this time since there must be an unusual mutation in HRV1. It will be interesting to see if I can learn anything more specific about Sarah's possible origin when/if a subclade is assigned.