The idea of a holodeck is that it's a simulated reality centred around you. In fact, many, most, or all of the simulated people in the holodeck may not be conscious observers at all.
So, either I am one of 6 billion conscious people on Earth, or I am the centre of some relatively tiny simulation. Winning the lottery seems like evidence for the latter, because if I am in a holodeck, interesting things are more likely to happen to me.
As you say, when someone wins the lottery, all 6 billion people on Earth get the same information. But that's assuming they're real in the first place, and so seems to beg the question.
I'm not yet seeing that other peoples' consciousness per se is relevant here. All that matters is that there be a vast pool of potential winners, conscious or otherwise. All that I (the winner, say) observed was that one of the members of this pool won.
If my prior belief had been that every member of the pool had an equal probability of winning, then I have no new evidence for the holodeck hypothesis after I observe my winning as opposed to any other member's. I would have predicted in advance that some member of the pool would win that week, and that's...
In passing, I said:
And lo, CronoDAS said:
To which I replied:
There's a certain resemblance here - though not an actual analogy - to the strange position your friend ends up in, after you test the Quantum Theory of Immortality.
For those unfamiliar with QTI, it's a simple simultaneous test of many-worlds plus a particular interpretation of anthropic observer-selection effects: You put a gun to your head and wire up the trigger to a quantum coinflipper. After flipping a million coins, if the gun still hasn't gone off, you can be pretty sure of the simultaneous truth of MWI+QTI.
But what is your watching friend supposed to think? Though his predicament is perfectly predictable to you - that is, you expected before starting the experiment to see his confusion - from his perspective it is just a pure 100% unexplained miracle. What you have reason to believe and what he has reason to believe would now seem separated by an uncrossable gap, which no amount of explanation can bridge. This is the main plausible exception I know to Aumann's Agreement Theorem.
Pity those poor folk who actually win the lottery! If the hypothesis "this world is a holodeck" is normatively assigned a calibrated confidence well above 10-8, the lottery winner now has incommunicable good reason to believe they are in a holodeck. (I.e. to believe that the universe is such that most conscious observers observe ridiculously improbable positive events.)
It's a sad situation to be in - but don't worry: it will always happen to someone else, not you.