In English we very often say that something 'has happened', so 'a lion's escaped' should be acceptable - some of us English-speakers actually live in England!
It might be that you contracted "has" that's the problem. Generally when writing you can contract "is" to 's but not "has". (When speaking we obviously contract words a lot more).
Does it work if you write "a lion has escaped?
Vraiment, c'est un catastrophe!
Quelle catastrophe ! → Une catastrophe (feminine)
In english we would normally say "what a catastrophy"