You've sent the school your degree. Did you send them a signed contract as well? They may want you to pay a fee to release you if you have. I don't know why else a Hogwan would 'hold' a degree, save for the fact that returning it is simply an expense they're not willing to bear. Did you offer to pay the postage if the school did send it back? Maybe you can do that C.O.D.

If you've not sent a signed contract, I don't think it's a big deal if the Hogwan keeps your degree.
Just go online to your own university's website and order another copy. I've ordered one this way. From the time I sent (electonically) my request, it took my uni about two weeks to send the new copy from the US to Bangkok. It was sent in a nice, sturdy envelope to boot.

If you're going into surgery, you've got plenty of time to get another copy. And don't just order one. Order three or four. In TEFL, You never know when you'll have to throw one or two copies of your diploma to the wolves while searching for new jobs.

This is another bit of info newbies can use. TAKE MULTIPLE COPIES OF YOUR DEGREE AND TRANSCRIPTS when you go overseas to teach. I brought three copies of my diploma and about 6 copies of my transcripts when I came, plus I ordered two extra copies of my TESOL certificate when I graduated from my TEFL mill.

I've heard too many stories like yours not to come prepared.

Hope this helps.

SS