Getting references after a company closes - any advice?

The company closed and I am not sure how to reach former colleagues. There are 10 people counting on me, so I am trying to be careful. HR only confirms titles and dates. Who did you use?

Thanks for writing this out. I went through something close to it last year, and it got easier once I kept a simple log of every call and form.

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.