We can't find it. Lost or OB? When does the three minutes start? Can I throw a provisional?

Lost or OB? Decide that first

If the group agrees there is compelling evidence that the disc came to rest out-of-bounds, play it as OB under 806.02.C. There is no three-minute search in that case: take the OB penalty and relief and move on (see where to play from after OB).

If you are not sure where it ended up, it is a lost-disc search.

The three-minute clock

Under 805.03 Lost Disc, the search lasts three minutes, starting when you arrive at the spot where the disc is believed to be. Announce that the clock has started so everyone is on the same page, and the whole group helps look. If the disc is not found in time it is declared lost.

A lost disc is one penalty throw, and your next throw is from the previous lie (or from a lost-disc drop zone if the TD set one up).

When a provisional is allowed

809.02 Provisional Throw lets you play a second sequence in two situations: when a ruling is unclear or disputed and the group wants the TD to decide later, or when the status of your disc is unknown and a provisional saves backtracking after a possible lost disc, OB, or required relief.

You must declare why you are throwing the provisional and which sequence of throws counts for which outcome before you throw it. Throw a provisional the rules do not allow and it is scored as a practice throw.

Not allowed: a provisional because you are “thinking of abandoning” the throw, or because you “might have missed the mando” (809.02.D). Those are decisions, not uncertainties, and you make them at the lie.