Full Idea
A fact is a thought that is true.
Gist of Idea
A fact is a thought that is true
Source
Gottlob Frege (The Thought: a Logical Enquiry [1918], p.342(74))
Book Reference
Frege,Gottlob: 'The Frege Reader', ed/tr. Beaney,Michael [Blackwell 1997], p.342
A Reaction
It strikes me as pretty obvious that facts are not thoughts, because they concern the contents of thoughts. You can't discuss facts without the notion of what a thought is 'about'. If I think about my garden, the relevant fact is aspects of my garden.