I'm very sorry to hear about this theft. That REALLY sucks! Have you contacted the owners of the company you contracted to work on your house? I'm sure there's nothing that can be done about it now, but they should have a record of which of their workers were at your house that day, and perhaps narrow it down. Although nothing short of video evidence would do much good, especially if the boss him/herself took it, or if the knife is 'in the wind' already.
Maybe do a review of the company on Yelp, or with the BBB, and mention that somebody from that company stole from your house.