It is all about RNG. You can increase the rate if you like to. Go to your PZ's "Zomboid"-folder (save area), look for the "Better Lockpicking" mod or for the mod ID "2368058459" and browse to this file:
".\media\lua\server\BetLockItemDistributions.lua"
Those numbers in there are the multipliers by chance. crank them up by 10 times or so, and you may get them, but keep in mind, the new value applies (as a fast bandaid) only to unvisited areas. Everything else being visited so far will take some time to respawn (according to your game world settings).