"I don't even know where Detroit is," said one bewildered-looking party-goer last night in the Sheraton Park's Florentine Foyer. He was at reception given by the Republican National Committee for the new Republican members of the Senate, and nobody seemed to know where they were, either.

"No, I haven't seen any of them -- I've been very busy," said Republican National Chairman William Brock. "Have you seen any of the new senators?" he asked a friend, who hadn't.

"I hear the Taylors -- pardon me, the Warners -- are coming, but I haven't seen them," offered a helpful bystander.

"The problem," Brock explained, "is that we have four parties going on in this hotel right now, and I hear there is another one over on Capitol Hill." Another problem was that the reception was held across town from Capitol Hill, just before the delivery of the State of the Union Message.

A few of the 11 new Republican members of the Senate may have popped in to say hello before running back to work, but only one stayed long enough to chat for a while: Sen. Roger William Jepsen of Iowa, who has his own ideas about the state of the union. "We have a lot of problems, both domestic and with foreign policy," said Jepsen. "The president seems to mean business in holding the line on spending, and he's going to get lots of help on that from my side of the aisle."

"Maybe more help than he wants," suggested a bystander, and the senator smiled.

Otherwise, the party chitchat focused mostly on Detroit, which has been chosen as the site of the next Republican convention, and on the up-coming presidential race.

"Dallas lost twic this week" was the least objectionable Detroit joke going around the room. A Mississippi delegate, Clarke Reed, gave one version of the most objectionable:

"They say that the convention center in Detroit is only five minutes away from all the hotels. The trouble is that nobody has ever made it."

There were no jokes but plenty of muted enthusiasm at one of the evening's other parties, sponsored by the Detroit Convention and Visitors Bureau. Detroit boosters hustled to attach a Detroit symbol -- a small, cloth picture of a vintage automobile (perhaps a Model T) -- to the lapels or ID tags of anyone who would stand still for it.

"It will be good for Detroit, which needs all the help it can get," said one guest at the Detroit party, "and it won't make any real difference to the delegates. Once you get into one of these conventions, you never get out-doors again until it's time to go home."

Brock thought it was too early to speculate on who might come out of the convention as the Republican candidate. Ronald Reagan's name seemed to be mentioned most often by others, but one delegate noted that the convention will be in Gerald Ford's home territory land siad, "He can get the nomination if he wants it." Sen. Edward M. Kennedy (D-Mass.) was mentioned as the most likely opponent. and nobody seemed very happy at the thought.

"We needn a candidate with charisma," said one kansas delegate, "and I don't see anyone with charisma coming up."