Invention bench toys keep disappearing

[cathyknits]

I've found that if I store an invented toy in a toybox, it will vanish after a while. I'm not sure how long "a while" is as I don't open the toybox inventory that often, and I also know it didn't happen last time I had an inventor sim in a family with a child (which was, admittedly, a long time ago).

Is this happening to anyone else? Does anyone know of something I might be able to do (beyond the obvious "don't put the toys in the toybox") to keep the toys? Or should I just count on making new ones from time to time?