Javelin of Serendipity

{w}Requires attunement
This magic javelin rides fate like a cresting wave.
It functions like a non-magic javelin and is
unaffected by spells such as Detect Magic,
Identify, or magic that achieves the same effect.
When you make a thrown weapon attack with
this weapon, rolls of 2-19 are treated as though
they are a roll of 20. Additionally, regardless of
the outcome of the roll, the javelin will be lost.
Precisely...(See Handout For Full Description)