User blog comment:The Milkman/Skyrim's Smorgasbord of Shortcomings/@comment-24.1.40.103-20130901215047

Sibbi Black-Briar isn't frozen in time. There is a note in the stewart of Riften's room that says he's not to be released until Maven says so. God knows how long he's been in there, so he might've just lost track of time.