Broadcasters pay hefty fees to use satellite services and additional fees to be included in Sky's Electronic Programme Guide. Unless there's a technical fault it seems likely that Family Radio's research shows that there are insufficient listeners via the Sky platform to justify the costs.
If Family Radio has only opted out of the EPG, you should still be able to get it by manually tuning your Sky box. Instructions here:
http://www.skyhelp.tv/sky-manual-tuning
The frequency is 12607, the polarity is V, with a symbol rate of 27500 and an FEC of 2/3.
If Family Radio has completely removed its services from the Eutelsat 28A satellite you will no longer be able to receive it via your Sky box but you can still listen online here:
http://www.familyradio.com/temporary/timezone_2/findTimezone.htm
Chris