Matthias Zeitgeist commented on Carsten Germer's article in Game Design and TheoryI use a similar random method. But my absolutelyNoTicketFindable depends on how lucky you were before. Example: There is 20% Chance to find a ticket, in other words 1:5 Chance to find a ticket. Every time you don't find a ticket I add, lets say, 1 to the numerator (2:5, 3:5, 4:5, 5:5). Now depending on when you find the ticket the absolutelyNoTicketFindable will change depending on the numerator. If you found it with 1:5 chance. The next 5-1=4 times you won't find a ticket again. If you found one with 4/5 chance. The next 5-4=1 time you won't find a ticket again. This works very well with higher chances, but not as good with very low chances.