Although it's entirely possible Aiden could have been turned, there's a strong possibility he can still be trusted.
I believe that Aiden was, in fact, saved by the Healer on Night 1. I believe the Healer then subsequently contacted him and told him that he had been saved. I believe that this is in fact what happened. Yes, it is possible that he could have been lying--as we all know, Aiden likes to be a troll sometimes--but my logic goes like this:
Let's assume Aiden lied, and say that the Werewolves really targeted someone else--let's call them Person X. Now, we know the Alpha can't use their ability until Night 2. There were no deaths on Night 1. That means there were only two possibilities: either Person X was protected by the Bodyguard or saved by the Healer.
Let's say that Person X was saved by the Healer. The Healer would have been told that Person X, not Aiden, was targeted, and therefore would have known with absolute certainty that Aiden was lying.
However, let's say that Person X was protected by the Bodyguard. The Bodyguard would not have known that Person X was targeted, and would have assumed Aiden was saved by the Healer. The Healer, meanwhile, would have been told by ThatRPGuy that no one was targeted, and would have assumed that Aiden was protected by the Bodyguard.
But here's the important bit--the werewolves would have no way of knowing which of these two possibilities had happened. For Aiden to come out and claim he was attacked if it had not been the truth would have been, if he was a werewolf, an extremely risky gamble: there was exactly a 50% chance he could be caught in a lie. If I was a werewolf, that is not a gamble I would want to take, especially when I'd have nothing to lose by remaining silent. Therefore, the fact that Aiden did claim he was attacked tells me that he was telling the truth--especially since nobody challenged him. Either he got really lucky and Person X was protected by the Bodyguard--or he's telling the truth.
Therefore, I find it odd that anyone would be suspicious of him--at least prior to Day 2. Of course, it's possible that any one of us could have been flipped, and sadly, there's no way to know except by sheer trial and error.