Bankruptcy Law Questions? Ask a Bankruptcy Lawyer.
If the contractor files bankruptcy, you'll be an unsecured creditor, which means banks and other parties that have secured loans (collateral) will take precedent over you.
If the debtor has any money, you'll be entitled to some pay, but if not, you'll probably lose a good bit.
IF there are any jobs in which the owner has not paid the contractor for your work, you can have a stop payment notice issued to the owner. This will result in the owner paying you directly instead of paying through the contractor.
You should probably speak to an attorney in your area about taking care of this soon.