Presumably, someone signed a receipt. According to the article, it was done on a Visa payment card.

Home improvement isn't exactly cheap, so I would hope people doing such things would be reviewing their receipts, particularly if they're in the business of constructing homes.

You would be frightened and amazed at the lack of paperwork on every level of construction.

Sometimes the receipts are tracked, but often it's a "well we charged enough to cover our costs and we got what we needed to do the job, all good".