Ghostcards

ghostcard (noun)
ghost·card /ˈɡōst-kärd/

1. A postcard believed to have been sent by a ghost, often arriving without a return address, postmarked from a place that no longer exists, or signed by someone long dead.

2. A souvenir from a haunted location that carries the lingering memory, folklore, or presence of the place, whether supernatural or imagined.

3. (Informal) A message from the past that unexpectedly finds its way back to you.

Example Usage:

• "I picked up a ghostcard from the old mining town. Whether it came from the gift shop or the other side is still up for debate."

• "Every haunted road trip deserves at least one ghostcard."

Etymology:
From ghost (Old English gāst, spirit) + card (from postcard), first appearing among travelers who insisted the best souvenirs were stories they couldn't quite explain.

See also: hauntmail, phantom post, spirit stamp, aftermail.