If a user has deleted an artifact by accident, the restoration procedure should be as follows:
1) Locate the most recent backup. This is in the ARTIFACTORY_HOME/backups folder for Pro and the HA_HOME/backups folder for a cluster.
2) Make a copy of the individual repository folder (example: /artifactory/backup/backup-daily/current/repositories/ext-snapshot-local)
3) Prune the copy of all files and folders that you do not want to bother trying to restore. Keep the metadata for the artifacts you do want to restore
4) Go to Admin -> Import & Export -> Repositories and under "Import Repository from Path" select the repository under "Target Local Repository" and browse to the pruned repository folder in the "Import From Path" field.
You can alternatively just find the file in the backup and re-upload it via the Deploy tab.