If the unregistered user misses the edit ad link emailed to them, how can they edit or delete the ad without admin intervention?

There are plugins those can help (like Item Password)

Besides the "Item Password" plugin, which has no password recall function, what else can help? (With code recall).

Auto-registration plugin can help too.

This plugin is for account creation. I am looking for a solution for the user who does not have an account. It's probably an issue to see in a future version of Osclass or a plugin. For now the issue is resolved with the intervention of the administrator, this is not a correct solution when there are thousands of posts.

I do not expect it would be issue as in last years no one needed enhancements in this area.
Most sites will anyway rewuire registration due to spam.