You may notice that the number of calling cards in your inventory is going down. The calling cards of residents who left SL were supposed to have been removed once the resident was "no longer with us" (RIP). They weren't removed immediately, but we are in the process of removing them now.
The number of calling cards DOES have an effect on the stipend system, but a very small one and shouldn’t radically affect your financial situation.
Soon, all the calling calls that do appear in your inventory are for current residents so that should make it easier to find your friends.