You've lost your original.bin????
If so you should still be able to dump the hacked firmware the same as an unflashed drive. Just run
dsam 1234567 12345
You will be able to copy the key by opening that FW in toolbox.
If you,ve got a friend who has the ms25 original.bin from his FW dump or are lucky enough to find the ms25 original.bin somewhere, flash the drive with original firmware.
After you have a working 360, dump the original FW and build your hacked FW from there.