This is why we recommend making unwanted applicants inactive rather than deleting them. There's a chance you'll want to consider them later. More info: How do I remove an applicant from the hiring process?
The only way to add a deleted candidate back to your CareerPlug account is by finding their information outside of CareerPlug (for example in your email inbox) and uploading their information back into CareerPlug. For example, some clients get Daily Applicant Digests, which contain applicant contact information and resumes. More info: How do I get daily updates about who applied to my job postings?
If you can find the applicant's information from a Daily Applicant Digest, you can upload their information via your Applicants tab. More info: How can I add a candidate who didn't apply through CareerPlug to my Applicants page?
It is possible that an applicant you are looking for is marked as inactive and may perhaps be stored in an inactive job. We suggest searching for the applicant by name using the search bar at the top of your Applicants page. Another option is to open up your filter options to view all applicants, not just active applicants from active jobs.
Are you sure you really deleted the applicant?
To do so, click the More Filters option on the right side of your Applicants page, then select the 'Show All Jobs' and 'Show All Applications' options and click Apply Filters.