Missing 2.2 GB of space on my micro SD card

I pulled my micro SD card out of my phone (LG G3) and inserted it into my PC (Kubuntu 14.04). I was in the process of moving several large video files off of the SD card onto my computer. Moving these videos would have given me 4.0 GB of free space on my SD card.

As the process appeared to finish, I encountered an error that said the last of the files (2.5 GB) could not be deleted (from the SD card). And my file manager could not access the directory (/DCIM/Camera) that held the video files I was moving.

I safely ejected the SD card, then re-inserted it. Everything appears fine and the video files I was moving are all apparently gone. However, there is only 1.8 GB of free space on the SD card, not the 4.0 GB of space that there should be available.

How do I recover this missing free space? I would prefer to use my Linux desktop tools to do the job.