Johnny Rotten

A "natural" explanation would be that, in the first instance, the song was actually playing on the extreme periphery of your hearing. I've done that a few times myself. I start humming or whistling a tune for no particular reason, then I'll realize that it was playing in a store or other location I was just in. I wasn't really paying attention to the music while in the store -- Instead, my mind was on other things, or I was distracted, or I was drowsy because it was the morning (and I'm not a morning person). Music can re-inject itself into the front of your consciousness after getting deposited, even partially, in the back of your mind.

In the first instance, there might also have been a television nearby playing the commercial, or a car radio playing the song as it drove by your window.

Also, as a regular poker player, I can tell you that probability ebbs and flows. Sometimes you'll get a string of "hits" then a string of "misses." It averages out over a sufficient period of time, but as RCAlyra and Zyr note, one tends to remember the "hits." For example, try to remember all the times you've passed under a street light that didn't turn off. You can more easily remember all the times it did, I'll wager. (No pun intended )

Sometimes the hits will be extraordinary. I still vividly remember one Hold'em hand where everyone left at the table (four people) had pocket face cards. And on the other end of the spectrum, through the dozens of times I've played at that table, I have never seen quads (four of a kind).

__________________
"The idea that money doesn't buy you happiness is a lie put about by the rich, to stop the poor from killing them." -- Michael Caine