I'll keep this simple because I have no info at this time, I'll update the thread as I get more info about it, but some guy in the Fender subreddit posted a picture of his Strat in a nice studio, but in the background I saw a Rhodes. A quirky looking Rhodes with orange stripes, a really low profile top and wooden sides. Could it be? Really? How?
Take a look at the photo, let me know what you think. I can't believe it's just sitting in a Studio and no one has documented it.
Pic -> https://ibb.co/54gYWQL
Post -> https://www.reddit.com/r/fender/comments/ulvfzo/can_ya_date_it/?utm_source=share&utm_medium=ios_app&utm_name=iossmf
:o
Good eye seeing that was a Rhodes! Unfortunately, on closer inspection it looks like it is the Rhodes Electronic Piano :(. However, the similarity is no coincidence as Mike Peterson (designer of the Mk IV) actually designed the case for the Rhodes Electronic Piano first and it had a direct influence on his design for the MK IV.
Here's a link to a more detailed look inside the Electronic piano: https://chicagoelectricpiano.com/rhodes/rhodes-electronic-piano/
Link to the MK IV on the Rhodes super site: https://www.fenderrhodes.com/pianos/mark4.html
Hopefully it will appear again someday though. The MK V 88 was a similar "lost unicorn" that was rediscovered so its definitely possible :)