This actually happens a lot in my game. I play rotationally so I have adults with laptops in their inventories, teens with homework books and children with toys in their inventories. When I play and travel to a community lot, I often see these other sims using their laptops, playing with toys and doing homework and it's very common that some of these items are left behind. Then when I switch households I find that my sims are missing items, very often children missing their homework book or their favourite toy. There are toys lying randomly on the sidewalks, sometimes I've even found my stuff by accident but things like homework books are usually lost forever. I don't know if they're despawned somehow or is it just that I can't find them. This is super annoying though.
I have a café in Evergreen harbour and I've found like 4 tablets lying around in there, I can't be sure if those are owned by sims or are they spawned by some NAP and then left behind when sims randomly reset (like they do quite a lot these days). Sometimes they leave stuff in tables in a way that makes the café gameplay more difficult because the items take up seating places and force the customers to eat standing up. I wish there was a way to identify if an object is owned by a sim and maybe even make it possible to send it back to that sim via mail or something. Better still, sims would not leave stuff lying around. (but they will...) On the other hand it makes places look more alive when kids do their homework and such. But I hate childish adults playing with their toys in restaurants/anywhere so.. I guess the jury is still out on this one.. :D
edit: I have a tip for you all if you find this as annoying as I do! They don't cost much so just buy like 5 homework books for each child, teen and university student. That way you can always do homework with your friends without having to worry that they don't have a homework book. With the lost toys there's not many other options than to cry but at least you could name the toy with that child's name so you can recognise it if you happen to find it again. It's kinda hard to tell apart all the purple fighter action figures lying around in parks and sidewalks without name tags.
