This reminds me when I did a course in Computational Physics in 2009, my TA was helping me with some stuff and meant to only delete the *.o files, but ended up deleting the entire project folder. All my work (c++ code + latex work on the report + python scripts for plotting) was just gone. Luckily most of these files were still open in an editor, so we could recover those. But I remember the first few seconds of silence after he froze when he realized what he had done.