what important plan did G have to remind L of because he had forgotten?

George reminded Lennie of their plan to meet by the river if Lennie got into any trouble.

".....Lennie raised up on his elbow. His face contorted with thought. Then hiseyes moved sadly to George’s face. “If I get in any trouble, you ain’t gonna let me tend the rabbits.”

“That’s not what I meant. You remember where we slep’ last night? Down by the river?”

“Yeah. I remember. Oh, sure I remember! I go there an’ hide in the brush.”

“Hide till I come for you. Don’t let nobody see you. Hide in the brush by the river. Say that over.”

“Hide in the brush by the river, down in the brush by the river.”

“If you get in trouble.”

“If I get in trouble.”