Just be patient. They will come. Here is some hints I have found:
If you have level 3 Exploration, you can see collectables and mushrooms on the map. But be sure to refresh the map about every 30 seconds.
Collectables and mushrooms still appear, even if the game is paused.
Theres maybe more hints, I just can't think of anymore right now. though, there maybe some hints in the VV2 guides.