to truly understand this read the thelater part of the article: https://loverofpiggies.tumblr.com/post/179920202990/ask-error-my-ideas-on-how-it-would-have

It had been an accident, Sans had found himself in a strange AU called the waiting room.

It looked like a large cafe, but empty of life.

He'd tried to leave, but seemed to be stuck.

Hopefully the others would find him soon, sighing he sat in one of the plastic chairs and quickly fell asleep.

"Being lazing again?" a voice asked amused, Sans woke with a start.

"Geno..." he said in shock, taking in the familiar white garb monster with red scarf thankfully without the large gash, sadly his other eye socket was still.. melty.

"Hello Sans, you really shouldn't be here," Geno said, with a sigh the other monster sat across from him.

"Geno, where have you been. You just vanished, everyone's been worried. I knew you were alive, we share a soul after all?" Sans asked worriedly, it had been years since Geno had vanished.

"Sans... I should have listened to you," Geno whispered.

"Yeah whatever, come on lets go on, Papyrus and the kid are waiting," Sans said.

"Sans you have to stop looking for me," Geno said softly.

"Geno, I found you I don't have to look anymore," Sans said annoyed, jumping to his feet.

"Sans, this is the waiting room. You can meet people that have no longer exist or not even born, I\m just a memory of what was," Geno said climbing to his feet.

"Where's the real you then Geno, its time for you to come home," Sans said, Geno gave a sad smile and started walking away.

"Stop looking Sans, remember me as I was not of who I am. I'd rather not destroy memories," Geno said, and snapped his fingers.

"Geno wait!" Sans yelled.

But no one answered.

He also wasn't in the waiting room AU anymore but home.

"Damn it Geno," Sans said angrily.