According to the Armory's archives, Sybil and a weapon arrived at the Armory in 1790, from a town named 'Mystic Falls'. However, Mystic Falls was not founded until 1860, meaning that it was impossible for the shipment to arrive from there and be noted as being from 'Mystic Falls'.
When Stefan becomes human, all of his compulsion was erased and the compelled's memories returned. However, in Silas' case the compulsion wasn't erased because he was technically an Immortal, not a Vampire.
Additionally, Alaric's compulsion on Elena should have been undone when he became human thanks to the Travellers' spell around Mystic Falls.