It would be funny if he's just a normal engineer somewhere who did this as a quick side project and won't come out as the creator because he's too embarrassed that he lost the keys.

Embarrassed is one thing, at this point he’d be putting himself in mortal danger

No way that paper and implementation is a "quick side project". Even if Satoshi were some kind of Bill Joy, Jeff Dean, John Carmack hybrid that's a full time endeavor

I may be wrong but aren’t their a significant amount held from day 1 that haven’t been moved?

To be clearer: that people would give away 10k of them to buy a pizza indicates back then they were seen as essentially worthless, meaning you'd probably not take much care to preserve the ones you mined for a while while playing with the software you wrote.

A lost key would explain it. Maybe that was your point.

If money didn’t move, that may be because the owner didn’t want it to move, or because they couldn’t move it bascule they lost the access key.

From an outsider’s perspective, both look 100% identical.