Thanks for all of the replys. I guess what I mean by search was what Nomad just mentioned as "hasty" search. Here is the story:

A trip of about 10 of us went on an overnight backpack, half of which were backpack leaders with up to 20 years experience in leading groups. After most of us went to sleep, two stayed up chatting. The weather was clear with temps reaching the upper 20's overnight. The next morning we noticed one person gone after visiting his tent to tell him what time we were breaking camp. This person was one of those that stayed up the night before. His sleeping bag was put up and his toilet paper was gone so we thought he may have gotten up early and gone to the bathroom. As time neared to break camp, we realized he wasn't coming back on his own. About 4 less experienced people went up and down the trail a half mile each way blowing whistles for about 30 minutes. Nothing. We stood around still thinking, and finally the leader with the most experience decided he would go look. He was headed down the trail, blew his storm whistle once or twice, and then in the distance we heard our friends yell for help. It gave me chills when I could clearly hear his yell. My heart sank, but at least I knew he wasn't that far away. Within a few more minutes we heard the leader searcher yell at us to start walking down the trail so two of us went down the same way until we saw them off the trail a bit. Finally, we all met up. Turns out, the person had gone to the bathroom before bed and got lost. He was out all night in 20 degree weather with no food and didn't get much sleep. I bought a storm whistle right after that trip.

I know each case can be different, but was wondering about minimal guidelines to use in case it ever happened again.