Getting references after a company closes - 11 months and counting

The company closed and I am not sure how to reach former colleagues. There are 14 people counting on me, so I am trying to be careful. A colleague offered to vouch for me. Is a client acceptable?

Ask former colleagues and supervisors in a short message and give them a summary of the job you are applying for.

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