Player forgot to place battlefield and has drawn a starting hand in high opl

Game Loss if the opponent catches it now; Warning + fix if the erroring player self-reports and the game state can be restored.

Battlefield placement is part of Start of Game setup (CR 113, 170.2.b) and must happen before turn order is decided and hands are drawn (FAQ 8541). Forgetting to place one is a Deck Presentation Error (TR 703.4 — same category as submitting an already-used battlefield, 703.4.a.1). The remedies are timing- and reporting-based: caught before opening hands → restore and proceed with a Warning (703.4.b.1); self-reported by the erroring player after hands are drawn and easily fixable → restore and proceed with a Warning (703.4.b.2); caught by anyone else after hands are drawn → Game Loss (703.4.b.3). At high OPL the downgrade clause (703.4.b.3.a) doesn't apply — it's limited to casual/competitive OPL.

Two things a judge should still do in every case: the battlefield must be added to the Battlefield Zone (treating it as blank or playing without it has no rule support), and if the game has progressed to the point where restoring the state isn't possible, the penalty upgrades to Game Loss regardless of who caught it (703.4.b.4).