Callback need to load a ticket's CF value from DB, not web form

In my callback for Modify.html, I need to know what the value
of a custom field was set to even if it was unchanged on this
particular form submission.

What I am seeing right now is that if the value was not changed
on this form submission, the value shows in the callback as
an empty string, so I need a function/method that I don’t know
about yet, hence this call for help.

Modify.html/jblaine

my $x = $ticket->LoadCustomFieldByIdentifier('Foofield');
my $xx = $ticket->CustomFieldValuesAsString('Foofield');

Both ‘x’ and ‘xx’ log as empty strings when I modify a ticket
without touching Foofield (Foofield DOES have a value that was
set previously).

So, cool, fine, Foofield was not modified in this transaction.
I still need to know what its value is from the database in
order to perform some logic if someone is trying to resolve this
ticket.

How do I load Foofield’s value from the database?