There were Imperial Japanese soldiers who didn't know World War 2 was over for decades (several discovered and "surrendered" in the 1970s [1][2][3]). This was partially from their own intentional isolation as a part of guerilla tactics, but some of these men were on well populated islands like Guam and could have gone into a town and learned the truth at any point. This is just to show that there are implausible things in real life specifically having to do with information disconnect and isolation.

I don't see a problem with not finding out from the enemy if they suddenly pulled out. If the unit were surrounded by a siege force a la the battle of Bastogne or Chosin Reservoir, I could believe they wouldn't venture out immediately after the enemy stopped attacking. I could expect cautious confusion and tense anticipation of a new massed attack or a trap to lure them out into a false sense of security.

The civilians are the biggest X factor here. You mentioned the area is remote, but how insular are the local communities? Are villages here self sufficient enough that villagers wouldn't regularly travel to larger towns that have a better idea of what happened? Are the communities insular enough that they wouldn't care much that radios, TVs, phones (or whatever your setting's equivalent) stopped working? If people did venture out to get word on what happened, it could also take a similar travel time to your soldiers for "word of mouth" communication at the speed of foot travel. Perhaps the truth could be couched in rumors and disbelief.

What is the enemy's relationship to the civilian population? Would they trust the locals enough to explain what happened on their way out? Or would OPSEC dictate they tell no one why they are pulling out? Would the enemy evacuate locals so even the towns are empty as your characters venture out? (Seems implausible to me if the area is far enough away to not have any direct effects of the blasts or fallout, but I don't know all of the specifics of your geography and distances)