Geany: disk full, file truncated

I was working on a text file in Geany under Debian. When I went for saving it, it said the disk was full. So I freed some space and retried so save. This time it said the file on disk was newer. I thought because it wasn't able to save so it wanted to restore the old content (it was fine to me). Instead it loaded a completely empty file! And I found no way to recover the previous content! Even "undo" didn't work. I still have the editor opened: is there a way to recover the original content?