Five years ago I lent a large sum of money a man so he could open a
business.  The business went under and he defaulted on the loan.  I
heard he filed bankruptcy, but I never received a notice of intent to
file.  Where do I find public bankruptcy records so I can know if this
guy filed bankruptcy and if he even added me to his list of creditors?

You must go to the location where he filed bankruptcy.  Bankruptcy is
a federal cause of action, Thus you will need to go to the federal
court house.  Often they have a "public terminal"(computer station)
where you can access the bankruptcy court records by simply typing in
the name.

If they do not have a public terminal you will have to ask for help
from the clerk.  You can get a the list of creditors from the case
photocopied for a fee of around .50 cents a page.

Most of the Bankruptcy Courts are now on-line but usually their case
records only go back a couple years.

A side note:  In nearly all States there are "Statute of Limitations"
on recovering your money. You need to move fast.