Two months ago, when the U.S. 6th Fleet began conducting hostile maneuvers off Libya's coast, European diplomats here suggested that an American air strike against recently installed SA5 missile installations was unlikely because of the risk that Soviet advisers working in them would be killed and a superpower confrontation might follow.

As many as 6,000 Soviet military personnel were estimated to be in the country, many of them working with the SA5 antiaircraft batteries.

Now some of those same diplomats are wondering where the Russians were when the installations got hit by American warplanes on Monday and Tuesday.

There have been no solid reports of Soviet casualties, from here, Washington or Moscow.

Some diplomats here now speculate that the Soviet presence in Libya, or at least at the SA5 sites, was overstated. Others believe that the pinpoint accuracy of the American attacks, aimed at the radar unit that serves as the missile's eyes and ears, was so targeted as to avoid causing Soviet casualties.

But one European diplomat suggested another theory: "If they really attacked these SA5s, they were probably sure that the Soviets were not there." Asked where he thought the Soviets might have gone, the diplomat smiled, and suggested, "A coffee break."

This suggestion, that the Soviets had been alerted, could not be confirmed here.

Although the Libyans are described as jealous of their control over the weaponry in this country and reluctant to allow the Soviets to maintain too strong a presence here, it appears unlikely that the Soviet advisers would have been completely excluded from the SA5 installations.

The diplomats say they believe some Libyan technicians were trained by the Soviets before the SAMs began to arrive in November. But in other countries where the missiles have been installed, including Syria, Russian technicians have continued working at the installations for years after the missiles became operational.

The theory most current in Washington is that the nature of the American strike was so limited that it greatly reduced the chance of injuring Soviet personnel in the area. This is supported by reports from residents of Surt, the site of the two American attacks, many of whom have told diplomats here that they heard either nothing or very little happening at the time that the American strikes were supposed to have taken place.

The SAM installation at Surt, unlike one at Benghazi, is not visible from the road. One diplomat said that the installations are spread out on seven square miles of land and, as a result, a pinpoint strike would not cause widespread damage.