I'm looking for A Slave To My Heart by mia_a03. It's a thorki fic, where Loki's punishment is to be a slave to the palace and have everyone forget who he is. Odin, the caster and the only one who remembers him, ends up in odin sleep and Thor becomes king. Thor has eyes on Loki and makes him his personal slave, all the while not remembering that they were once brothers.
It's really well written and very heart wrenching, especially when Loki meets Frigga and she doesn't remember who he is at all.
I've been searching for a copy of this for awhile. I had missed the window on her announcing her departure from the fandom and subsequent removal of all her fics. I've read it but hadn't saved it since at the time it was a wip. If anyone has a copy please please pm me.