So the problem is that avrdude doesn't decode the .hex into a .ino file. Good luck with that. I believe you could use a disassembler after converting the machine code into .asm, then you would get C code. But there are no programs out there (AFAIK) that will convert back from .hex to .ino.
The IDE exports a .hex and retrieves a .hex. It does not open the .hex. However, when you still have the original compiled hex, the IDE may just compare it to the one taken from the chip. But when there is nothing to compare it to, the IDE cannot open it. The IDE does not and cannot open a hex file.