A long time ago when i was young...

I remember a day when i was young like 2013.

It was night, i dont really remember the day bcs that was a long time ago.

My grandma is dead since 2011.

I remember that i saw something. It looked like my grandma. I remember that i told my mom and dad and they said that i have imagined it. I know i didn't... It was too real. I just am watching reddit threads and i just thinked abt this moment. Can someone explain this?