I don't know how many casinos have "temp" cards, but I've seen 3 uses of such cards.(Some casinos also used "introductory cards", which meant you had to earn a minimum number of points before receiving a permanent card. These are different from "temp" cards.)

1. Temp cards that a slot host carries and presents to players that are playing the slots without a card. The slot host takes some preliminary info (player's name), inserts the card, then invites them to come to the player's club booth to get their personalized card. (Some slot tracking systems include software that will alert a slot host if a machine is receiving regular play without a slot card.)

2. Bus group (or other travel group) temp cards -- when a bus group arrives, the passengers are each handed a temp card. The passengers can play immediately, rather than standing in line at the players club and burning up limited time at the casino. At some point, the players get a permanent card. It also helps track the incremental action that the bus company brings into the casino.

3. "System down" temp card -- this is an unusual one. When the players club software is down, the club has temporary cards to give to players. When the system comes back up, they can merge the temp card points into your regular account. I have a temp card from the Riviera that was used for this purpose, from a prior software system they were using. It may have been from a batch processing system that had to be taken off-line for updating. This one's an unusual use. Doubt that many casinos use temp cards for this purpose.

I'm sure there are other uses for temp cards.