Looking for a place to resign
1) he simply committed an oversight,
2) he desperately attempted a speculative move to turn the tables, hoping for the opponent's mistakes, or
3) he sought for an appropriate opportunity to resign in order to shorten his agony (and secure the time for a drink, usually paid by the winner).
It is considered impolite for a third-party commentator, who is often at a lower rank than the player, to declare the move was an oversight or the player hoped for his opponent's errors. In such cases, this expression is used: "He probably sought for a place to resign".
Example of 3) above, from 'First Kyu', the novel: "A high ranking player, in a losing game, often plays a move which obviously does not work. On seeing the opponent to correctly respond, he resigns. This custom is commonly referred to as 'looking for a place to resign'. Yong, staring intensely at the corner, must have picked it as his place for resignation... The time he was taking now was to prepare himself for the loss of this all-important game."