Thanks for posting this, this definitely sounds like odd behavior.
After looking at the preview link, it looks like there are no elements or styles on the blog post collection template page. Did you remove the content here?
No way! My design is gone! It’s the third time that happens to me in a site. My internet has been killing me for these last few days. Does intermittent internet connection affect that? (I suppose it does)
If you have consistent network outages, it may cause this sort of behavior. The Designer might not have been able to save any changes you made.
That said, you may be able to restore to a previous version of your site. Can you please check your versions to see if there are any instances with these styles?
Before doing this, you can manually create a backup version of your site as it is now by pressing CMD + Shift + S (ctrl on windows).
Thanks in advance, and I’m standing by for your reply.