First
Fact = Truth, so those who say there is nothing true in this life should not use any word which represents truth or reality, am I right?
Second
Somethings need a source and somethings do not need source, the sayings and words or definitions need a source.
Other things which do not need a source are the things we observe and these things we can not say it is not true.
Third
If I do not have the evidences or proofs on my table that there is a country called Canada for example, does this mean that Canada does not exist?