I've tried to find a similar report made on this topic, but can't find exactly what I'm talking about. So, in this game I wanted to move my sims into a bigger home which meant a bigger lot, I had some objects on the lot I didn't want to lose so I added them to my inventory. Then I bulldozed the lot so I could get more money back and move to a different lot.
When I was starting to furnish my house, I started to place some paintings my sims created, well, the first few painting were just white. I go into live mode and all it says is scrap painting. So, I go back and place more, now they're just straight up disappearing. So now I try different LIVE MODE OBJECTS and they disappear too. However, this is not that case for build mode objects like decoration, plants, furniture etc. This is only the case for objects that are obtained/created from live mode.
For instance I have some photos that my sims took and a graduation photo. I don't have any other sim made/obtained objects to try, only paintings or photos. But I do have some career/event obtained objects that appear just fine.
This only happened after I moved my sims, before these kinds of objects were in my inventory and they appeared just fine. I've come to a conclusion that this is not permanent, I had some small painting that were also disappearing but they appear after you undo and then place the painting again, but I still find that this is a bug. I still have a few large paintings that completely go white and won't show the actual thing. In short, these objects do appear again after some time, but some paintings are still bugged and some people may think they've lost their stuff at first glance, just like me, I thought I had lost these things for a few minutes of trying over and over again to get them back.