Its a multi tiered answer as to where has everyone gone.

It is interesting because the labor shortage is across all industries, its not just shite jobs no one wanted. we are talking accounting and finance with the same shortage as a mcdonalds.

First we have a large set of the population that was nearing retirement age. We have an aging population and have had a aging workforce for years. so you see some of the missing labor coming from that subset. Now this would mostly mess with the corporate and say accounting jobs at the very top levels for the most part.

Then you have the population of women that left the workforce to provide child care because daycares/ fricking schools have become absolutely not reliable to be open due to the sniffles. These Woman are more likely in roles that would require in office stuff and they aren't there anymore. How many come back? who knows, people have learned how to spend less and stay home.

Next you have the young generation- college age kids and high school kids. They aren't filling in the low income jobs like you would expect and the basic waiter/waitress jobs. I think this is primarily due to the lack of shame of living with mommy and daddy.

The puzzling piece is the older staff/young management being a vacant part of the labor force- again probably tied to the lack of shame of living with mommy and daddy. People that use to move out and have their own lives now just stay at home and when you live with mom and dad probably no bills, no need for any job.

The first group likely is never coming back at any decent rate.

the second group could fully end up back in the labor force at some point or near it thanks to Biden flation

The third group who knows what they do.

The last group probably comes back at least some what.

I also wouldn't be surprised if of the online economy/ side hustles are actually pulling more and more people in.