I presume you had the code that is why you could use the spare keypad.
With the keypad off - wouldn't it be simple to plug the interface into a PC and run through 9999+ codes in a few seconds.
The keypad has no interface to plug into, the code is 6 digits, it locks out after several wrong codes, it takes 10 minutes for it to be used again. The other issues is the cable is embedded into the keypad and unless you cut the cable it does not come apart.
If I have a keypad that has failed and nothing I do will get it working, I will cut the cable then use my diagnostics tool (that I made) to interface with the cable and use that keypad to open the safe.
I have a lot of experience with electronic safe locks, each manufacturer is different, every opening technique is different. I have a tool box filled with different electronic safe locks to assist me opening different safes.