In its rush to close down the Community Services Administration, the Reagan administration almost forgot one thing: to get the agency's deputy director confirmed.

On June 8, the White House announced that President Reagan intended to nominate Samuel J. Cornelius, president of a business management and public relations firm, to the post. But it didn't get around to sending the nomination to the Hill until Sept. 28, two days before the agency was scheduled to shut doors.

Aides polled Senate Labor and Human Resources Committee members and found no objection to clearing the nomination for the floor. The Senate had until midnight last night to confirm Cornelius before his agency expired.

The Senate earlier had cleared the nominations of four other agency officials. Committee aide Barbara Mulkey said she assumed the White House was going ahead with the last-minute nomination for Cornelius' sake: so he would be able to put his presidential nomination on his resume.

A White House press aide had no explanation for the four-month delay other than to say, "It just takes time. There were probably just some extra checks and clearances. Some take a few days, some a few weeks."

Cornelius, who has been working at CSA as deputy director-designate since June 1, professed not to be fazed by the delay. "Nobody at the White House said nothing to me. Nor did I even get concerned.