Yeah, Pleschinski even includes the Émilie detail and quotes from a letter she wrote to a third person, in which she expresses how much Voltaire's behaviour is bothering her ("I don't recognize him anymore"). It's just that this comes right after he writes that Voltaire "went to Bayreuth without the King". But the itinerary at Trier (no idea how reliable) says they went together as well, so. ...thinking about it, it might be a simple mistake and Pleschinski actually means Brunswick, which Voltaire did visit alone on his way home.

One of my reasons for asking was that apparently, some of the letters from around that time don't exist anymore, and since it's exactly when the blow-up happens that leads to more than two years of radio silence, I was trying to piece together some more details beyond "Fritz is insulted that Voltaire didn't stay for good" and possibly politics. (And what with the ungratefulness and "only come back with the works I'm owed", I was also wondering in how far not getting the Pucelle played a role, given that he started writing postscripts like these - La Pucelle! la Pucelle! la Pucelle! et encore la Pucelle! Pour l'amour de Dieu, ou plus encore pour l'amour de vous-même, envoyez-la-moi. - on his letters during the first half of the year. So if he found out that Voltaire gave it to someone else in Bayreuth... On the other hand, I'm pretty sure we would know about that, because surely Fritz would have mentioned it.)