Wow, I did not realize some have had this since 2014! Anyway, I only recently had have this problem. Seems like it started after the Day of Dead patch. I don't know about frogs because the save I'm actually trying to complete all collections in already has all the frogs so I stopped collecting them. All the previously spawned frogs are still there. Rocks are not spawning in any neighborhood besides the one my Sim lives in. In his save I had only played his household and never any others.
Some background history. He started life in in Willow Creek next to the Bargain Bend empty lot. He was a Tech Guru for career. Then I had him quit his job and move into Bargain Bend to see if he could survive by collecting alone and began to build him a house bit by bit. He was able to do pretty good so I decided to have him move to the biggest lot in Newcrest and began building a new house from scratch with the idea that I would now keep and display one copy of each collectible. I built his living areas from premade rooms available from build mode and began building display rooms for his collectibles of my own design. I also wanted to "collect each type of rocket through game play so I finally had him marry and move in Liberty Lee from the BFF stock house hold since she is in the rocket career. I figured I would have her complete both branches of that and unlock both career rockets while my main Sim finished out his collections.
Anyway, since in his early days he had sold most of his collections to survive, I had to go re-find some of the same ones he had already collected so I could have a copy for display. About two weeks ago it seemed the rocks were getting harder to come by and then they finally stopped last week except for in his current neighborhood. I was about to have him join the scientists career as I figured there would be all those rocks on that lot at least at first but then I had another idea. Over the past couple days I went and started playing some of the other households. I systematically played one household from each neighborhood in Willow creek for one Sim day each. Each time I played a household in a new neighborhood at least some of the rocks would spawn within a few Sim hours but I did not collect any of them. At the end of the Sim day I would put those Sims asleep, save the game, and go select the next family to play. The rocks that spawned seem to be persisting so far, so tonight I'm about to return to my Sim and go collect all the rocks that I can.
This is kind of a work around but only for residential neighborhoods. You can't really do this trick for the park in Willow creek or Oasis Springs or the Ruins in Windenburg. I'm not even sure if the problem will effect the science career lot yet as I haven't played my scientists save in a while so I don't know what happens if you collect all the rocks from that area. Hopefully this info helps at least a little.
"Rocks are not spawning in any neighborhood besides the one my Sim lives in."
This is how the game works since launch, spawners of any type are only "active" when you are actively in the neighborhood. Rocks typically takes 12 to 24 sim hours to re-spawn, so if you wish rocks in other neighborhoods spawn, have your sim visit those neighborhoods as many as possible; they will eventually appear when the countdown completed.
Hope this helps.
