Data recovery cannot always be done on a running system. It's always a smart move to reboot using Disk Drill's Data Recovery Boot Drive and proceed from the minimal OS X boot from USB. Make sure the drive with lost data is completely disconnected. Get to any Mac, and download free Disk Drill. Install and launch it. Choose "Create Boot Drive" from the main list of available tools and follow the instructions.
Disk Drill Basic is free and features unique data protection algorithms: they are Recovery Vault and Guaranteed Recovery. In case of accidental data loss, if enabled, they ensure your hard drive recovery runs as smooth as never before. Recovery Vault is your database of file parameters that are not recoverable with a deep scan. Guaranteed Recovery is your extended Trash that always stores deleted files before they are gone for good, even on SSD drives with TRIM enabled.
With all the data recovery, data backup, disk management and optimization features Disk Drill becomes your all-in-one stop to perform disk imaging and secure data recovery at any time. Disk Drill is a well-known product available for multiple platforms for years.