Getting references after a company closes - first time posting

The company closed and I am not sure how to reach former colleagues. I would rather hear the honest version than the polite one. HR only confirms titles and dates. 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.

Thanks for writing this out. I went through something close to it 14 months ago, and it got easier once I kept a simple log of every call and form.