My guess is the clue is in the multiplicity of the Mudcat servers.
hudie
sonny
etta
etc

occasionally I find posts don't stick, and watch for that, copying the text to clipboard in such conditions. BT (notso) HotSpots compound this.

I have found that you can use the back button but............

If your thread goes to the top, you may (I do) assume your post has taken. But........

what if two people post to the thread simultaneously? Given that there is a latency in "sending" - packets arrive asynchronously so the header packet may arrive after the text, and the same is happening to the other peoples' post (how many peeps?). But someone wins out, the thread is updated, and you think it is because of you. After all, the preview was perfect, wasn't it?

with three (or more) servers I can see yet more cobblication, and I have to say I wouldn't trust BT's CDN (Content Delivery Network) to be failsafe. Other CDNs are available!

What made me think of this was a non-post last night on a more (relative term) robust connection - still BT but not a HotSpot.

My recommendations:
1) Check it is your post, then just as back-up:-
2) keep a copy of your text
   a) on clipboard or
   b) in a text editor like notepad
3) Thank Max for 'Cat when things go smoothly (but keep yer options above).