In my story there is a generic fast food restaurant that is well known and otherwise normal. In the last year, new franchises have opened up. They are completely legal, licensed, owned, incorporated, etc.. The paper trails exist for a lot of documents and are too good to be forgeries, but as far as witnesses are concerned they could have been planted after the fact. However, there is no evidence some of the ones made this year were actually made. There is no evidence that money was paid to create them. There was never a construction site, it was always a lot yesterday (occupied by unrelated business or abandoned) then a renovated or fully built, staffed, and opened restaurant the next day.
What organizations (e.g. FBI, FDA, IRS, Insurance, etc. real and/or fictional) would notice this (occurring once or as a pattern) and investigate? What sets them off?
The year will likely be between 2000 and 2040 and there is no public knowledge that anything supernatural exists (indistinguishable from the real world). The emergence of some of the new restaurants this year are supernatural in origin but organizations not associated with looking for supernatural phenomena will 99% of the time not even consider supernatural explanations.