1. You have to figure out the URL to the thread which can be easily done by mousing over it or right click link properties
2. See how many replies the thread has (xx replies)
3. Paste the URL into your browser
4. Add a period after the URL(.)
5. Add the total number of replies (URL.xx)
Hit go or enter and this will display the very last post in the broken thread and will allow you to use your normal edit buttons to either fix it or delete it.