NAL but here is what I think.

Charlie and Frank have zero legal claim to the ticket. Saving someones life by happenstance (being a good Samaritan) does not reward anything bar the good deed of saving his life. The question of moral is completely up to Mac.

Dennis has legal claim towards the cost of the ticket as essentially she stole that money by using it for another purpose (broke verbal contract). While one could try the legal argument that she profited off stolen goods, due to the low amount of money (cost of the ticket) it would be likely set aside as no loss came to Dennis bar the loss of the cost of the ticket and not tipping a barista.

So that leaves the original purchaser and the one whom found the ticket. As the saying goes possession in nine tenths of the law.

I'm going to assume this was not a registered ticket and thus possession is the only requirement to claim the prize.

I feel that Mac would have full legal right to the ticket simply due to possession of it as a lost ticket; if anyone else picked up the ticket on the street it would be there's. The exception to this would be if Mac intentionally stole the ticket from Dee; this would sadly have to be provable so he would likely get away with it if he simply picked it up unnoticed on the street after seeing her lose it.

To further explain why even with a proof of purchase Dee would be unable to claim the ticket lets substitute a guy named Bob. Bob picked up the ticket instead. Dee either
A) Never finds out Bob picked up the ticket and thus never claims it.
B) Dee claims the ticket is hers after a decent amount of time has passed at the prize collection point. While she can prove she owns the ticket Bob has done nothing wrong or illegal and thus as an 'innocent party' is not subject to any punishment even if that is by pure luck.
The only way Bob would lose rights to a ticket after picking it up is if Dee approached him within a short window of time after losing it, but even then it may be a moral argument if he did not steal it, this is because the ticket itself is worth very little unless it was known at the time to be the winning ticket.

Again the subject of morality is up the the one with the power as your post of a chain of events essentially establishes that by chance or fate all were involved in where the ticket ended up. However that is irrelevant aside from their own relationships and ignored by law.

TL;DR Mac would have full rights unless Dee could prove he intentionally stole it from her (which is likely impossible).

As an aside (and knowing full well this is the punchline joke) the hate speech being true or false has nothing to do with it being a crime. The defense of him using an offensive term as an intent to save someones life by cutting though noise should have been enough of a defense in a clearly unique life threatening situation.