Unsubscribing to Private Lists

[MegaBran20XX]

Some time ago, I subscribed to Wil Wheaton's block list. While I like the idea, his list was a little too cumbersome.

Unfortunately, he's since made the list private. It no longer shows up under my subscriptions, and I can't access the list itself directly, but all of the blocks remain in place and are even listed as being part of a subscription attached to him. There doesn't appear to be any way for me to unsubscribe.

Sorry if this is a duplicate or if I'm just ignorant. Any help is appreciated as removing thousands of blocks manually doesn't strike me as an appealing afternoon(s).