We occasionally had whole SOG recon teams disappear while on missions in Laos or Cambodia. Sometimes they were involved in firefights and on the radio calling in air support when the radio went silent,and sometimes they just flat went silent for no known reason. No radio contact,even with choppers flying over their AO looking for Orange panels and listening for survival radio contacts.
I am not aware of a single time this happened we didn't send in another6 man recon team to try to track them down or find evidence leading to what happened to them. This was crazy dangerous because the NVA were expecting us to insert a team to try to find them,but I am not aware of anyone not being willing to go look.
AFAIK,not a single SOG MIA was ever recovered. Not even a body. Teams did find bandages,spent rifle shells (empty cases),and blood,but no bodies and no live soldiers.
I do know of one case were the sole survivor of a recon team that walked into an ambush was rescued a day or two later,but we all knew that same day he was alive,and working on evading the NVA search teams. He used his survival radio (same as the ones pilots carried) to keep aircraft circling out of hearing range updated on his plans,and a day or two later he figured he had escaped and called in a slick to pick him up. A month or so later he was back out in the jungle again,leading his own team.
SOG also received intel from a captured NVA prisoner about a NVA POW camp in Laos that held,IIRC,3 US pilots that had been shot down. We put together a rescue mission,but Ambassador William Sullivan was the US Ambassador to Laos,and refused to allow us to go that far into Laos to run the rescue operation. We had everything in place to do it,including a fuel resupply already positioned in Laos for the helicopters to refuel so they could make it back,but Sullivan killed the operation at the last minute. The US Government had the names and serial numbers of those pilots,and AFAIK they were never seen or heard from again. No doubt the NVA executed them when they closed the prison camp down.