They're writing conventions that were never really properly letters. This is evidenced by the fact that they don't have Old English names like thorn, eth, ash, etc. They appeared later in the language with the advent of printing presses to save time and space and aren't really properly separate letters that we "lost". Particularly the ampersand, considering that it's used today - and isn't really a letter despite what the jackass who did the video seems to think.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*