[asdfasgasdgasdg]

Seems like you could fix this issue by generating a random salt for the unique ID and placing it in local storage. Never send the salt value to the server, but incorporate it in the unique ID. This would keep the uniqueness property, but eliminate your ability to reverse the computation to retrieve PII.

[mekkkkkk]

Wouldn't that just be a contrived session ID?

[asdfasgasdgasdg]

I'm not sure exactly the definition of a session ID, but maybe? It would be what I described, and if I described a session ID, then yes.