would you have waited to see what would've happened or would you have taken a chance and given them a new queen and let them have a clean start? I am assured that if you opened the hive and saw so few bees in it you'd have done more than put the lid back on and hope for the best.
That's what I did. Almost three weeks after queen cells erupted, I saw no eggs or brood in my cutdown split, so I decided to re-queen with a bought marked queen. Before installing, I checked agains, saw no queen, eggs or brood, so I pout her in. She was released in 3 days, and when I re-inspected a week later, I found eggs and brood -- and the queen. Not my marked queen, though. The best I can figure was that a virgin queen was in there all along, waiting to mate and/or prepare herself for laying. It did take her about 4 weeks to get rolling, and the bought queen turned out to be for naught.
I do view it as a $19 insurance policy, though, to ensure that the hive would thrive. And this all occurred earlier in the season, before then season hit full flow.