Jeeze, I apologize for constantly talking about correct usage, but some phrases are really jarring to read. 

The meaning of the phrase 'long shot' is well understood; it means an unlikely guess.  Maybe someday it will be written 'longshot', but nobody does that yet!  In the case of some phrases, the single long word, and the two separate words (e.g. everyday, vs. Every day; alright, vs all right; anymore vs. any more) the different things mean something slightly different.  Longshot, though, isn't yet a thing. 

Kay