I downloaded the game today and once it finished i began to play. I closed the game once i was done and decided to come back and play some more. I could not find a gw2.exe file anywhere on my computer so i am being forced to download it again. Is there something i missed, somewhere it could have hidden on my computer, could this issue happen again and if it does what can i do about it?
It seems highly unlikely that your .exe file would vanish just like that. Are you talking about the actual .exe file or a shortcut on your desktop?
The only thing that I can think of is that an anti virus program removed the .exe file.
What I would do if I were you is, copy that .exe file the next time just in case, and wait and see if it happens again. We cannot answer the question if it can happen again with "no", because it's highly likely that it will happen again, if you did not remove it yourself.