If you delete a Behance page within Adobe Portfolio, it does not delete the project on Behance. If you wish to re-import the deleted page, the easiest way is to toggle the integration off and back on again.
To only import that one Behance project:
After you've republished your Project on Behance, it will automatically appear within your Adobe Portfolio editor in your Default Collection and in Manage Content.
Note: any changes made on the Adobe Portfolio Page that weren't updated on Behance will be lost – the current Behance Project will be imported.