How would anybody know you had the cash? Its not like you carry it in your hand... But yea,,,
If there is an auction, sometimes they offer escrow service for a small fee, that way if you find a car, you just go to the auction office and seal the deal and they cut the seller a cashiers check. At really big shows some offer title services and such as well..
I've also just checked to see if my credit union had a branch close by then call ahead that you will need a large cash withdrawal on such and such a day to close on a potential auction.
They have always handled it cheerfully..