Responsible employers do keep such records, but mostly as pre-emptive defense against litigation. Somewhat strangely, it's a GOOD sign if the phone interviewer is reading from a script. It means they take seriously the idea of being fair to all applicants and asking them the same questions. Some are better at hiding the script than others, but personally I confess it up front and explain that it's to make sure we don't favor some applicants over others in our questions.
While I do not doubt at all that age discrimination exists, it's not universal. The last five people I have hired were all mid 40s and up - 3 definitely over 50 IMO (obviously not allowed to ask although things like graduation dates give clues) and in the 5 companies I have hired people for not one has ever by word or action hinted I should bias myself against people by age, or any other criteria really, unless you count one that wanted a stable work history and lots of experience for one particular role, which I suppose shows a bias against the very young.