Odd glitch

[#1]

I was making a post with a picture and had just clicked post - up pops the note "Someone has beaten you to it" or words to that effect.
So using my normal practice I used the browser back button to get back to the forum.
This is where it gets odd - after leaving the forum and going to TBB I came back to make another post and when I posted it the picture from the earlier backed out post was embedded in it.
Any thoughts on why this should have happened.

[#2]

Honestly - No idea at all.
Not something I've ever seen.

[#3]

Possibly the form data for the image isn't linked to the post but your session and is only cleared when you post?
You can try and recreate it.... if you have nothing better to do

[#4]

I will - the next time I post a bit slowly