As title, it's persisting. Tapping it does nothing. Possibly relevant is that I lost no troops fighting it but didn't take a screenshot because I figured that just happens sometimes... Screenshot contains part of a 68% revealed map. Spoiler
Hmm. I've had this happen before, but the monster spawned mid trip. It was a mighty kraken for me. It all went away post trip
Just had it happen again and you may be right, maybe it appeared after the journey started. Either way the corpse / wreckage should disappear after collecting rewards.
Kelani explained me once, I forgot. In a nutshell...don't count it...if it was not in ur path while u started ur exploration... Just a lil bug. Btw, only 68% ?