Houses/Lots Disappear

Just experienced what I think is this issue. I downloaded a lot from the gallery to renovate and add on a small business residential space to. I did so through manage worlds, so no sim on the lot. I finished the entire renovation and I got a server error when I tried to save it to my library because I'd already built it and lost it once and figured it was completely gone. So failed to save it to the gallery and decided to move my sim onto the lot to see what would happen anyway, and it loaded into an empty lot like before.

The weird thing is that I went into build mode and the original gallery lot came back. My additions and renovations were completely gone (which did include custom content but I'm not sure this makes a difference) and the original lot from the gallery was there in it's place right when I loaded into build mode. I decided to just add my addition (instead of changing the whole lot again) to see what would happen, went back into live mode and it's fine, and went back to manage worlds and back onto the lot and it's still there. When I did this addition, I did not include any custom content, I'm not sure that that's the difference but I thought it was important to note anyway. No error codes, no orange check marks, the map looked like my lot was there the entire time (I'm building on one of the empty lots in the new world), everything was normal until I moved my sim into the lot and hit play to go into live mode with her.