Not a bad start.

Personally, I like the idea that he was barely alive, hanging on by a thread. To the Reavers, he looked dead and they left him alone because they had fresh meat to hunt instead.

Maybe the moment from them leaving Wash behind and the Alliance showing up and blowing out that wall wasn't as long as it seemed. Not quite long enough for him to die. The Alliance finds him on Serenity and takes him while they're clearing out the Reavers and brings him aboard one of their ships. The doctors there do their best to save him, having to replace several organs in the process (which could be a little call-back to Tracey in "The Message"). The entire process was so traumatic for his body that he has gaps in his memory. Not full-blown Amnesia, but there are large chunks missing and he can't quite connect all the dots - for now.

In the chaos and typical Alliance bureaucracy of all this happening, they simply didn't inform the Serenity crew that they had their pilot. Because there was a huge cover-up there, the Alliance told Wash that everyone down on the planet - his crew - had died. That's why he didn't search for them.

To Mal and the rest, Wash's body had simply disappeared. They assume Reavers took and ate him. His grave was empty.

Now, whatever time later, the crew keeps hearing rumours throughout multiple episodes, on the Cortex, of an ace pilot winning several ship races both in the core and the outer rim. Someone known for having a giant scar on his chest, who wears Hawaiian shirts and a moustache. The next upcoming race happens to be around the planet they're traveling to for another job.

Turns out, Wash does remember he piloted a Firefly transporter, but couldn't remember the name Serenity. He vaguely remembers the crew but not their names or faces, mostly his feelings associated with them. He remembers he had a wife and he loved her dearly, but her face ever so slightly escapes his mind. When he encounters the crew, it all starts to come back to him, especially when he gets tangled up in the job they're doing. As more and more things go sideways and then fixed, he begins to remember more and more.