It absolutely exists; I lost almost all my balance because of that. twice now.
I got too many 7s in roulettts and lost too a few days ago.(lucky this one was a bonus code)
Edit: You got that 'Gambler's fallacy says that' part wrong. It is just the opposite.
If I were you, I would bet 7 when it hit 7 twice.
It is called luck, I usually use this strategies in dice, if I win, I would bet the same bet, if I lose, I bet the opposite.
I have successfully used this method to earn 10btc from dice within 1 week.

Any strategy is risky in luck based games. What was your original deposit that helped you earn 10 BTC?