The REST API returns a 409 status if the status is not "available," "uploaded", or "deleted":

http://logosdatabase.com/logoimages/77771764.jpg

However, the REST docs do not include this info. (I am adding it now.)

Also, the PHP code does not check for a 409 response. Patrick, I'll let you add that to OpenTokArchivingInterface.deleteArchive(), and have it throw an OpenTokArchiveException. (I will document it as such.)