Getting references after a company closes - 2 months and counting

The company closed and I am not sure how to reach former colleagues. I have been trying to stay organised about it. A colleague offered to vouch for me. Is a client acceptable?

Thanks for writing this out. I went through something close to it 2 months ago, and it got easier once I kept a simple log of every call and form.

Use a professional network to find a former manager. Many will still write a note.