Sims inventory vanishes when they travel.

I'm trying to do the events challenge, one of the tasks is to play with the stuffed animal in the sylvan glands. Problem is I can't do that because each time I travel it deletes ally Sims inventories, I can't build there to place one and have my Sim play with that one which I've had to do at the park. Now I'm stuck and have no idea what to do, it's really annoying to have my son's inventories delete anyway without doing this event.