As your career history lengthens it might be that companies or organisations you previously worked for no longer exist. They may have been bought out, re-branded or gone out of business. It is after all very important to tell the truth and include these organisations on your CV/résumé. You will want to show your continuous work history and include your roles and achievements within these businesses.
However it could also create a problem.
Who will a potential employer contact for a reference?
Who can be your advocate and speak up for you if the business is no longer operating?
Thank goodness for social media as it now makes it easy to trace former managers and colleagues from defunct businesses.
LinkedIn of course would be the most favoured site to contact and network with previous employees and it is simple to search the site to find them.
Once you have re-established contact you can enter into the dialogue that you may be needing a reference or support in a potential new role. Keeping a previous manager in the picture when you are job-searching is common-sense too. Conversations and networking with former colleagues is very useful for maintaining focus too.
It makes job-searching a little more practical and more effective.