I'm not sure about the rest of your questions, but I do remember that the original (fabricated) story was that she dropped her purse when leaving the store, and claimed that the ticket must have fallen out when that happened. So, even if it had really happened as she said, the person who found it couldn't have returned it.
A number of years ago, a convenience store sold a ticket to a customer. There was something wrong with the ticket (the wrong lottery game, or was supposed to be cash value, or something). The store's policy was to hold the ticket either for sale to another customer, and failing that, it was the property of the store owner.
An unsold ticket won the jackpot, and the clerk on duty pocketed the winning ticket. I had to do some searching, and found this:
http://www.newstribune.com/stories/020303/fea_0203030037.asp
The largest jackpot in South Dakota was a controversial $12.4 million Lotto America prize awarded in 1991 to Ionia Klein of Dallas.
Klein, who worked in a Gregory convenience store, first said she bought the ticket before the drawing. She later admitted claiming it the next day after realizing it had the winning numbers.
The ticket was left behind the counter two days earlier by another clerk who had punched it up for a customer who refused to buy it.
Store owners Michael and Diane Dacy and Scott and Julie Anshutz sued Klein for the jackpot. They eventually agreed to split the money; the owners got 58 percent, and Klein received 42 percent.
--- end cite.
This would tend to support your contention, although I think it's a little different, because there was an attempt at deception and I believe she violated a previous agreement about ownership of refused tickets (although the article doesn't mention it). I remember it, because I was living near there at the time.