I am in the pirate bay and I have used keys to unlock some lanes. Now I have only one lane left, which requires 5 keys, and I have only 3 keys. I am not sure if the key drops are in specific levels or just random. Should I keep playing random levels to get the drop?
If you have the latest version of PvZ2, the keys are no longer required to unlock doors. Instead, there are now 'World Keys' that unlock new worlds (I presume the world where Dr. Zomboss will appear). As of the latest update - you will know you have it if you can get the the 'Gargantuar' levels - keys no longer drop.