Mauritius Lotto tricked?

Among millions of numbers only the number which has been played only once is chosen. Algorithm malfunction or on purpose? Even the first Millionaire show had a million rupees winner.

The trick? One explanation is they might have painted the winning balls with a heavier paint than the others. Suppose you paint the ball number 3 with a 10g paint and ball number 4 with a 5g paint. Which one will be more likely to stay down according to probability? Aha!