Blank Texture's thumbnail is not blank???

I needed a small blank texture, so for the sake of time(lot rot good that did me now…) I resized an existing 1024x1024 .tga to 128x128, used the eraser tool(GIMP2.8) to remove what remained of the old image and exported it into my project directory.
In the editor the newly imported texture’s thumbnail displays the portions of the image OUTSIDE of the canvas of the newly resized image.

Ive reloaded the image in GIMP, and resized it back up to 1024, but there is nothing there.
I deleted it from my project directory, and re-exported but the errant thumbnail persists.
I suspect there is an editor specific thumbnail file somewhere that for some reason isn’t getting deleted when I delete the main file.
Where are editor thumbnails kept? or is something else going on?

Any help at all?