I can explain even that , let's say the chance to find that bunker is 0.001% chance per tick on world map so if i'm not wrong on average you would find 1 special encounter per 10000 ticks on world map. Though there is a chance very small chance that you would find it only after 15000 or 5000 ticks, actually the possibilities are endless how you can get lucky or unlucky , nor it's possible to calculate when you are going to be unlucky or lucky.
Then make a virtual coin its no weight and make 50% chance
Two times with same char?
And yes, Pandaed, you were essentially asking for gm/dev confirmation... When you asked for it, lul.