For a while in the early 2000s to late 2000s there was a very widespread usage of 4 and 6 replacing the ch and sh sounds. In hindsight, this was more likely to

For a while in the early 2000s to late 2000s there was a very widespread usage of 4 and 6 replacing the ch and sh sounds. In hindsight, this was more likely to replace the letters 'ч' and 'ш' than Latin letters. However it died out.