The last 2 days, any post I write, you can’t see its title, even if on twitter that it’s automatically posted, or on the dashboard it’s ok, when I open the main blog page there’s no title -only the description,if so.
I had the same problem with Twenty-twelve theme, titles were not appearing. It turned out that the theme supports different posts (Standard, Image, Quote, etc.). Title did appear on Standard style but not on Image or Quote style posts. Check if your theme has different styles and if in last 2 days you chose a different style.