If you were truly hypo (and you would have had to have blood tests for
that), rather than just some similar to the oxycodene side effects (see wikipedia), and
you had thyroid medication and
, then there is a good chance your hair will come back, after your hypo levels stabilised.
I think what has happened in your case, is that your pain relief medication, Oxycodone has had some issues in side effects very similar to being hypo.