Even with an emergency or going out of business, it would seem that a one-line note would help explain the situation better and not be too much of a strain to type.  Weird, for sure.

Email is always a preferred method of communication for me.  I always respond via email to the receipt of an order and want my own abstractors to do the same.  In a few instances, this email chain has been  critical in demonstrating the research problems and delays that we or our contractors have encountered.  I'd suggest being open and honest with your client with full disclosure.  Tell them the exact circumstances and that  you're operating in the dark with regard to the situation too.  Apologize for the inconvenience and offer to get the work done as soon as it is physically possible and see where it goes from there.  Put it in writing, telling them who the contractor was (if you are not constrained from doing so by any nondisclosure contract terms).

Offer a discount on their next order if you can (and on this one too).

Bummer.