Ok i found the problem why the deleted item was still in the index
We changed the settings of the following:
$SearchApplication = Get-SPEnterpriseSearchServiceApplication -Identity "Search Service Application"
mentioned in this post: Deleted item still showing up in search results if only doing Incremental Crawls
Only we didn't set them to 1 and 0, I set it to: 10 and 240.
Both properties needs to be true before removed from the index. 10 Crawls and 240 hours before it is deleted.