I know this must be a stupid question - updating a record

I am trying to update a record in a keyed file.  If I open the file in READ_ONLY
mode, I can properly find the record that I need, and print out the contents.

However, if I open it in READ_WRITE mode, I get no errors, but it does not seem
to be finding the very same record.  No exceptions are occurring, it's just
nothing is printing out.  My first thought was that maybe I didn't have
permission to write to the file.  However, I peeked at the permissions for the
file, and I see that my group has *all rights to the file.  Public has *change.

Any assistance you can provide for this 400 newbie would be greatly appreciated.
This has become the project straight out of Murphy's Law.

Amy