Ideas
OxterAne When you placed the missing appliances the first time, did you have MOO on? And did you use Alt when placing them? All those appliances are set up to be the only thing on a counter, but with MOO on, you can place other things alongside them on the same counter. If you reload the lot later with MOO off, many of those MOO placed object, including small appliance can disappear. It seems to depend on which object gets loaded first as the lot is being loaded but Idk for sure. I've had it happen a lot because I build my lots in a separate vanilla user folder and save them to my Library and load them into my main play save from my library. When I open a lot that I installed from my library for the first time, there is always something missing as I tend to clutter my kitchen counters with MOO on and use Alt to place some things, usually placing more objects than the game allows normally with MOO off. It happens in other places too where I've placed a lot of clutter. What goes missing is usually some of the clutter, but small appliances have gone missing too.
If you place things with Alt, then they are off grid and have a tendency to try to snap back to the nearest grid point if you grab them, but I think they may do that sometimes on loading the lot. If they can't place when they try to snap back, the objects can disappear sometimes. Appliances typically won't work as you getting a routing error if you place them with alt, but some of them will be fine. But if you also place clutter or another object on the countertop, then that can cause something to go missing the next time you load the lot as well.
Hope this helps.