according to this
https://endless-sphere.com/forums/memberlist.php?mode=viewprofile&u=50679
he last visited yesterday.
My guess is he decided to commercialize it and asked someone to remove his threads.
If this is the case, I don't think this should be allowed. Once you post an idea out there it's out there and should be kept intact--that's why we post here in the forum. You don't get to decide to unpost things completely--it's why we instituted "post history" so that when grumpy members wholesale delete their useful stuff you can still go back and find it in the history link, and restore it.