Contractor Issues ... Any advice out there?

So what do you do when your contractor repeatedly doesn't show up?

We hired a teeny contracting firm (read: two brothers and some guys they pay hourly i would guess) to do the drywall upstairs. They began work in mid-December. We were pretty happy with it, and I'd say about 85% of the work has been completed.

But now our contractors are MIA.

We last saw the crew boss on December 23rd. He said they wanted to work while we were gone on holiday, and we arranged for them to have access to the house. We were excited, expecting we'd return back from Christmas with the folks to the completed upstairs, ready for tile and flooring and such.

Yeah, not so much. In fact, they never entered the house at all while we were gone, nor made any attempt to do so. We were pleasantly surprised when one of the workers showed up on Wednesday and worked solo for a few hours. He assured Jason full crew would be showing up Thursday. He even left the contractor's toolbox in the workspace.

But since then, nada.

We've made several phone calls to the main contractor, all of which have gone unanswered and unreturned. Granted, New Year's eve was Sunday, we expected nothing to get done that weekend, but there was still Thursday and Friday, plus today (Tuesday).

Yes, they were the lowest bidder for the project, significantly lower than the other contractors. And we did not find them through a reference. But they've received half the funds for the job (the other half contingent upon completion). We're not sure what to do at this point. We already had to cancel the tile guy we had scheduled, and postpone an inspection. The backerboard has yet to be hung, and there's still some finish work to do (sanding, corners, etc.) Should we find another contractor to finish the job? Should we just wait it out and keep making phone calls? Has anyone else experienced this? Are we being too impatient? Are we just stupid?