If a player does not collect the rewards from a contract within a short time, a warning icon pops up over the business that just completed it. When clicking on the icon, a balloon pops up. The player is then given an option to "Ask for help" from neighbors or "Clean Up!". The former choice restores the contract when a neighbor visits and clicks on the building so that you will recieve the full benefit of the contract. The latter choice will automatically refund half of the inital investment you paid to purchase the contract.
When accepting assistance, any queued assistance offer can be used to recover an expired contract. Furthermore, assistance offers remain queued for around 24 hours from when they are offered.