Would records still exist of any search for a person (teenage girl) who disappeared from her home and family shortly after 1891? How may I find them?

[From Forebears Research] -- The Toronto Police Archives (accessible through the Metro Police I believe) should be able to help. If she was a minor, then the Children's Aid currently may know what existed then in this capacity. Beyond that, if she was found dead at some point there should be a coroner's report. There may be some school records from the time that could have useful details although not specifically to do with the search, rather info on her personally.
You should also check the newspapers in the area where she resided in 1891, as well obituaries, wills and other such events of the remaining family members.

Is there anywhere I can get information on St John's Anglican Cemetery, Ida, Lot 12, Con 11, Cavan Township. Can you please tell me what the Ida, means?

The 'Ida' refers to the town that the cemetery can be found in. I would assume from your question that you obtained this information from OCFA -- if so, visit the site as they give contact information for all the cemeteries they list in their database.
From L. Johnson -- Through my own research of family that is buried in any Anglican cemetery,whether it be a churchyard or not I have found the Anglican Archives in Toronto to be extremely helpful...especially if you know the date of death and if the people are buried in the said cemetery.

I found my ancestor in the 1871 census. There is a specific page number associated with the record. However, there were two other entries for that family name (believed to be his children) which were on page D. What does census page D signify?

[From Suzanne Schaller] -- My guess is that D = deaths. 1871 has a schedule on each township for "Deaths occuring within 1871." I *think* that the index uses D instead of a page number. The index is for head of household & strays, but I think that every entry on the Deaths page is also in the index.