Just from my own thinking ... I don't see how the police would have any idea who the rightful owner could be.
Say 350 people show up claiming the lost ticket ... what are they going to do? Only the lottery office would have the information and means to "possibilty" identify the real purchaser and that may not be a 100% sure thing, if no video exist ... there would computer information for the ticket but maybe the righful owner can't remember all that ... when and where purchased ... perhaps they are a heavy lottery player, buying tickets from many places.
I still would sign the ticket since it is a bearer instrument ... I would not hand over a blank unsigned ticket to the police or anyone. More than once, evidence has "disappeared" from the police, whether it be drugs, money or whatever.
If a person is going to go the police route then I would bring an attorney along as a witness or maybe a local reporter from a newspaper or TV studio to document everything ... but then you get yourself too much publicity which could be a problem.
I still think going straight to the lottery with the ticket signed and let it all play out is the way to go ... maybe still take an attorney along or someone to be a witness might still be a good idea.
I posted this earlier from the Illinois government with a lottery ticket being a "bearer instrument".
"Any unsigned Lottery ticket issued by the Superintendent is a bearer instrument and shall be treated as such until a name is imprinted or placed upon the rear portion of the Lottery ticket in an area designated for "Name". Once a name is placed on the rear of the ticket in the place designated for that purpose, the person whose name appears in that area shall be the owner of the ticket and shall be entitled to any prize attributable to that ticket, subject to the provisions of subsection (d)."
I would not hand over an unsigned found ticket to anyone ... I would sign it and hope for the best. It's not my problem that someone got "careless" and lost their ticket.
I would possibilty make an exception if the actual ticket owner did show up and if the prize money wasn't a huge amount and the actual owner was struggling with bills and a sick child and had other children to also care for ... I would maybe just turn around and walk out the lottery headquarters door ... but I would check it out first and if the prize money is a huge amount and enough for both parties ... then that might be the way to go.
In today's world there have been many scams of people saying they have cancer or a very sick child just to collect money donations and then the whole scam is revealed.
Those are all worst case scenarios ...
CW
Count it as a dog day (sometimes you're the dog, sometimes you're the tree) 
