Changing ID number

Is there way to change the ID number of a post? I had put in a new post on a blog and looked at it several times. The ID was https://office-organiser.com.au/blog/?p=42 and so I sent out a newsletter (on behalf of my client) announcing details of this post and then when I went back to look at it the ID had changed to https://office-organiser.com.au/blog/?p=43. So when anyone goes to the link I gave them, it says there is no post matching that criteria. How can that happen and why? I had done a copy and paste so there is no way I would have written the link incorrectly. Is there a way to change the ID number back to https://office-organiser.com.au/blog/?p=42?