There are some employees that work on Saturdays. There are recruiters that find candidates that fit the needs that they are looking for and reach out to encourage them to apply. The building is located in Findlay, Ohio.
The company has employees in India and the United States that work on the same accounts and out of the same systems. They likely were about to give you a job, but just needed to verify the employment.
This company is not a scam. It is a company hired by other companies to complete various portions of the recruitment processes. For some areas and some companies, there is no way to get a job without dealing with them. They are legitimate.