pick up a pin(идиома "See a pin and pick it up, all the day you'll have good luck. See a pin and let it lay, bad luck you'll have all the day" Alisa Beck)
take pot luck(I couldn't get any information from the telephone directory, so I had to take pot luck. • The only downside was we couldn't book so had to take pot luck in wether we could get a seat or not.4uzhoj)