Are blank stamped letters a bug or a relic from the past?

Question

I come here to your forums in the hope of finding some old players who may have information about this: I have a Stamped Letter, i.e., a letter that was at some point sent by the mail system. As we know, stamped letters cannot be edited, and to be able to send a letter to someone, the first line must be the nickname, right? Well, I have one stamped letter that is completely empty! There's no log of who "wrote" it nor the date. I know letters and writable items from before 2006 don't register the date of when they were written, and I heard that for a short period of time, even the name was not registered. But the first line of the body of the letter must be the name of the person you want to send the letter to, right? So it cannot be blank. I thought that maybe it's an item that respawns on the floor somewhere, but I failed to find anything about it online or in-game. Please, if someone knows anything about it, reply here!

Here is the images:

Thank you!