Experience requires reflection. Does the in-memory simulation contains a model of the in-memory simulation? If not, we are certain that it does not have sentience as we understand it.
Well, yes. I'm not sure about Pong specifically, but in many games with computer controlled entities, the game AI for each entity simulates what the entity "knows" about the world, which is different from the simulated world state itself.
(Also, at least according to Wikipedia, sentience is distinct from self-awareness. The former only requires the existence of a subjective experience, not necessarily self-reflection.)
I'm not sure I buy the "sentience without self-awareness" concept. First, defining it as "subjective experience" seems circular, and second, reflex actions like e.g. plants moving towards the light or reacting against a parasite would count as subjective experience; in the extreme, even a blind chemical reaction like fire could fall under that definition.
Honest question -- what do you think is going on inside of babies and children? Self-awareness as a developmental process is complex and relational, and takes many years. Our senses though are more or less put together by puberty, built up by simple interactions with the world.
Simpler animals like wasps and worms don't seem to have those, or have really simple versions; their behaviours look more like following hardwired programs reacting to specific conditions, not influenced by some inner "mind state".
On the other hand, it is not a knowledge of precision. You cannot predict exactly what thoughts you will have in the future or what ideas you will have before you have them.