The Sat Rad Player, which was billed as the first satellite radio player app for Windows Phone has now disappeared quicker than it appeared it seems. According to an article over at XMTuner, the SiriusXM legacy stream is down (no word on a temporary fault or a permanent halt of the service) which has led to the app being removed from the Marketplace.
Unfortunately, if it's the latter of the cause then there's little anyone can do, hopefully it's a technical glitch on their end and the stream resumes soon. We'll keep our eyes and ears open for any further detail on the issue.
Thanks for the tip Jonathan!