Who do I ask for a reference after a layoff? (update)

The company closed and I am not sure how to reach former colleagues. I have read a lot of threads here and could not find my exact situation. HR only confirms titles and dates. Who did you use?

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 last year, and it settled down once I kept a simple log of every call and form.