It was a hallucination, I'm not sure when it explains what happened but maybe it'll be in the side stories.
Anyways, I'll put it down here if anyone doesn't want spoilers ↓
It was a hallucination Kwonwoo's mind created. He liked Dowon before he lost his memory, but was scared about losing someone precious to him again so he didn't have the courage to try something with Dowon.
But as he wasn't able to control his feelings, he made the guiding calls an excuse to meet but at the same time didn't say or do anything because of his trauma. (He lost everyone he loved and their deaths repeated in front of him every day)
Because he cared and loved Dowon, he started to appear in his illusions just as his family did.
So he knew that it was an hallucination but he couldn't turn away from Dowon asking for help, that made him stop on his tracks and not enter the exploding building (I don't remember if it's an exploding building or something else, but it was the cause of his memory loss — which instead would be death or permanent both physical and mental disabilities if he didn't stop to save his hallucination of Dowon)
thank youuuuu i think i kinda get it now
was it ever actually answered as to why MC was seen before ML lost his memories the first time - when his mind was read? or was that just really a hallucination thing? im so confused