The Walking Dead featured an interesting plot twist when Michonne found an iPhone engraved with herself, a current version of Judith, and some Japanese symbols. The artist behind this design probably was not Rick, at all, though. While this seems to be intended as a message to Michonne from Rick, it is more likely that another character fans of The Walking Dead are familiar with is behind this iPhone's etching. Jadis, real name Anne, was known to be an artist on the series and was last seen flying away with Rick -- so it's not unlikely she is somehow creeping on Alexandria to get a look at Judith and providing messages to one person or another.
Of course, the Dead universe could simply credit Rick with drawing those versions of Michonne, Judith, and Japanese symbols. Maybe he has been taking art classes wherever he flew off to and someone has been showing him photos of Judith since she grew up and started wearing Rick's hat which was passed down to Carl and from Carl to Judith. More plausible: someone else drew these.
The Japanese symbols on the phone contained a specific message: "Believe a little bit longer." When framed as Rick communicating with Michonne, it seems to indicate that he is telling his family to believe he survived the explosion on the bridge and will come back to them as soon as he can. However, when you look at this as though Anne/Jadis is behind the iPhone and its carved images, it could be an encouraging message from Anne who has some sort of good intentions in helping Rick but ultimately put him in a situation which he cannot escape yet. The images of Judith and Michonne would almost certainly be enough to keep him going.
However, as far as viewers know, Rick can't read or write in Japanese, so there's some sort of blank which needs to be filled in with the dots in either scenario. Pollyanna McIntosh expects to reprise her role as Jadis/Anne when The Walking Dead movie rolls around, so it's not unlikely she is involved in this etching transaction in one way or another.
"The phone is obviously a hint at some larger story that took place," Kang said in an interview with Insider. As for what took place and how it all ended up on Virgil's boat, only time will tell, but Rick's location of "north" has now been confirmed as the universe finally starts to head in his direction.