It won't stay secret forever, secrets do not exist that way. People like to share, especially with friends, and they share... think of it like a brushfire, or a zombie infestation. It'll start small but the effect snowballs with time. Exponential increase of awareness? Anyway, just try and enjoy yourself while you can, before these 'special encounters' turn from being actually special, to just another farm mechanic, however distant.
And Good Luck finding something. The loot may be profitable, but the surprise is priceless.