Looking for a specific fic, fairly sure it came out post Avengers but before IM3 or Thor 2. Steve got Bucky back somehow but he wasn't clear what was happening around/to him and Steve reassured him using a specific phrase they'd had during the war to let the other know everything was ok. It was something along the lines of "it's all sixes and eights" and Bucky relaxed after hearing that.
Anyone read it? It was almost certainly on Ao3.