I had my snake do the same. She lazily struck the butt and 1/2 way coiled on the rat, this just upset the lrg rat and I had to intervene. But I killed the rat while she was still actively on it so while she balled up on the rear I finished of the rat for her and she took it, she may not have even known I did her dirty work. But I didn't want her chewed. You had tongs ready and did what I would have. If your snake didn't take it after, sometimes after a bad strike they can be intimidated or prey shy for a bit. You may try to pre kill and if they will still take fresh dead there is no risk of this happening.