Apple doesn't monitor your conversations.
Siri, on the other hand, does. To some extend at least.
Siri is responsible for a lot of things on your iPhone simply by guessing what you might want to do at a certain time, on a certain spot, in a certain situation, conversation and so on.
In your case, Siri probably "thought" that it might be useful to add the genie emoji to your Recently Used page in the emoji keyboard because you used a word that is related to it. That happens all the time, to everyone.
Or maybe it was just added by default to fill up the whole page.
I, for example, just reset my iPhone completely without restoring any backup but still my Recently Used page is fulled to the top with emojis I never used before or after reseting the device.
Hopefully that answers your question.