Been some discussion about if a lottery ticket is a bearer instrument so I checked with Cornell Law School.

"A holder of a lottery game ticket shall be deemed to have AGREED TO ALL THE RULES and PROCEDURES of the commission by the purchase of the ticket." and most state lottery tickets say something like by signing the ticket, the holder agrees to lottery rules and regulation.

There is also a discussion about proving ownership even after signing the ticket. Some are claiming state lottery officials will ask if the signer purchased the ticket. As usual, they show no proof which seems to be SOP for most claims made by people that never actually cashed a large jackpot ticket. 

IMO if I find a ticket that turned out to be a large jackpot winner, I'll contact lottery headquarter before knocking on their door. Doubt it's necessary for the holder to prove they made the purchase but a lawyer can explain our Rights.