1
Sign the back of the ticket. Right now.
An unsigned lottery ticket is a bearer instrument. Whoever holds it, owns it.
In most jurisdictions an unsigned ticket belongs to whoever presents it. Lost, stolen, dropped in a car park — it is gone, and you will have a very hard time proving otherwise.
Sign it. Photograph the front and back. Put it somewhere that is not your pocket.
The one complication: in some places, signing in your own name forecloses claiming through a trust or an entity later, which is how winners stay anonymous. This varies, it matters enormously, and it is the single best reason to spend twenty minutes on a phone call before you sign — if, and only if, you can secure the ticket in the meantime.