I know that sometimes a parent will tuck away something and forget they did it or where they put it. I know my mom had done that when I was a kid, later on she was going through a storage area for her sewing and found some old stocking stuffers she had put in there 4 years before for us. It wasn't anything exciting just some stickers and such, but someone else could have done something similar with toys.
Also people buy in bulk when there is a sale or clearance and they stock up for birthdays/holidays and say they pass away, or get sick so those just sit there in a closet.