Unable to relinquish personal plot

I am attempting to relinquish my personal plot of land so I can transfer server (ward 1, plot 27, shiva server), but I am currently unable to do so.

The reason for this is that a former tennant's chocobo is still stabled here. The character's name being Big Spider, and their chocobo named Burdstinian.
They are no longer a tennant, and haven't been for several months.

Their account has also been inactive for several months, and they claim to be unable to access it due to a lost authenticator.

There doesn't appear to be any way for the remove the chocobo myself, and I can't relinquish the land until it's gone.