Recover "forgotten" aliases/auto complete addresses?

[fhouston]

Hopefully this is the right place for this. How do you recover an address that has had the "forget" option selected during auto complete? In this case the address is a location that is being used in the calendar. To fully explain it we have a couple of conference rooms set up as "locations" for use in the calendar. They all have the form [location]-[size]cr@... So as the user would type the [location] into the attendee list on a new meeting all of the conference rooms at that location would show up. Someone recently mentioned they are no longer seeing all the rooms though so my first thought is they clicked the "forget" as opposed to actually selecting it one time. How do I get that back onto their list?