Getting references after a company closes - 18 weeks in

The company closed and I am not sure how to reach former colleagues. A colleague offered to vouch for me. How do you ask politely?

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.

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