Is your Sourceforge username actually benlumley? I've been trying to add both yourself and Pete as site admins but I can't add you as it reckons the user benlumley doesn't exist or you haven't activated your account.
The project audit log does show Rendle adding you as a developer, but there is no entry about you being removed so I can only guess that you didn't validate your email or something like that and you've been removed automatically?