Now you're going to second-guess the milk's intentions when it started eating that ringneck?? LOL!!
Actually, from everything that I've seen being said about the interactions between Lampropeltines and ringnecks here and elsewhere, it really doesn't seem all that hard to figure out the likely general scenarios:
1. milksnake much bigger than ringneck: milksnake eats ringneck
2. milksnake and ringneck roughly same size: found under same rock
3. milksnake smaller than ringneck: milksnake in danger of being eaten
That's just a rough guesstimate, of course, and may interact with the timeline for the development of the ringneck's venom (no, Jeff, NOT poison). I believe that some snake species are born with their venom glands already functioning, but I don't know whether all are or not.
As for being "on the menu" -- the snake ate it, so.....maybe in the a la carte section? 
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1.2 Peruvian rainbow boas (Amaru, Asiru, Kulipsa)
2.0 Brazilian rainbow boas (Arco, Olho)
1.3.1 Honduran milksnakes (Chicchan, Chanir, Chakar, Hari, Saksak)
1.0 Thayeri kingsnake (Coatl)
0.0.1 Mexican black kingsnake (Mora)
2.4.4 corns (Cetto, Tolosa, Uce, TBA)
1,000,000.1,000,000 other critters