i think thats why the end bit erin says if she knew she couldn't have faked it. He couldn't tell her cause everyone else would then also know he regained his memories and would ruin their plan to get rid of them all.Okay, he wanted to hide things from the elders, but there was nothing preventing Aiden from telling only Erin that he has regained his memories. If he did that Erin would had some comfort that Aiden was with her and not against her. Not only that, they could plan things together.
The prince should have smacked him harder.