Ouch! Sorry 'bout that. Choosing 'back' on your browser didn't work?
A login will time out in 12-15 minutes. If I've started a post and am called away, sometime I'll open another tab in my browser & log in just to make sure my posting window is covered when I hit 'send.'
Or, as you say, cut and pasting from a handy word processor works fine.
Karma to you!
[on edit: Time out! Having images too big for the classifieds software will cause an ad to disappear when you click send. The recommendations for max image size are in the steps for doing an ad. But they're also here
-- so be careful and it should show up.]