We actually still called the hotel, but after sitting on hold for 10 minutes (at $5 a minute from our non international cell plans), we opted to hang up and pursue the email route as Starwood had suggested.
Of little help now, but consider using Skype for these types of things - cheap international calling not only helps with entities that lack a domestic/toll-free number, but also calling certain call centers of international companies to your benefit. It's annoying to have to resort to things like Skype to get problems handled efficiently/cheaply, but it's helped me immensely.
In any case, it does seem to me that SPG really dropped the ball here, but nevertheless I hope that you are able to find satisfactory alternate plans for your anniversary.