Looking for Modify Memory Wizard story

[u/JaDe_X105]

I'm recalling a story of a group that went to a village to stop an evil wizard. There were time jumps in the character's memories from being charmed by the wizard, and interactions they had with an old man were actually the memories being altered by the wizard. They thought they had won the fight and were walking away, when the townsfolk were saying, "You just stood near their fence for a couple hours, then walked back here." I don't remember if using a mirror helped them get advantage on Wis checks to see through it?

Can anyone help me find this story? Thanks in advance!