At the very bottom left hand column of your Trulia search page, they indicate getting information from Public Records. Maureen is absolutely correct, your agent will also have to search using either City of Detroit Public Records (which may not be accurate) or Realist if they are a Realcomp user. They will be able to sort and identify all sheriff sales from the results. Results will include all activity including those mentioned by others.
I also suggest their results be from the Statistical Comparison data form of public records.
I wish you luck in selling your flip.
The manner of transfer is the key. From a Realtor perspective, a property needs to be a true comparable.
For example, if a home was foreclosed by a lender, that is a transfer. Does that carry the same weight as a property listed for sale in the MLS? Probably not. Yet it is a sale, and becomes a comparable.
If a family transfers title, say parents to children, that is probably not included as a "full value transfer".
90% of transactions are conducted through Realtors and the MLS. One of the key things to look at is the length of time since the sale closed. Appraisers normally use three to six months. In a shifting market a Realtor may use sales no more than a month old and take into account Actives and Pendings.
You could also ask your Realtor for a report from a local title company that would include non=MLS transactions.