mystiesmudge01 - this thread has been a lot of fun and I've learned lots too.
When I start a game I always get the wishing well and the tree of prosperity on the lot. I went through a very long phase of being more excited about the pixies you get from that combination than gnomes. Although I always did love to collect the gnomes.
I've read that people are having problems with the ToP at the moment. But I've not noticed it. Maybe they need the Wishing Well & ToP on their lot together.
http://s5.postimg.cc/can5151mv/Screenshot_510.jpg
This is one of my favourite shots of the pixies in the wishing well and my fairy making a wish. You can hear the pixies too if you get close enough to the wishing well. They appear early evening and vanish at 3 am.
My Sims were getting a gnome out of this wishing well almost every time I sent one there to fish. And sometimes I'd find them there autonomously fishing. The gnomes usually appear in a small treasure chest that the Sim opens and the gnome goes into the Sim's inventory.
You have to check their inventory periodically to see if there are any new gnomes in there.