Hello everyone i am a dm and i gave one of my players a killer longbow from a series of of magic items known as the killer weapon series they crit on an 18 through 20 and I am pretty sure they came out in EGW but now I can't find them anywhere I know they exist because I can see it on my player's character sheet and I remember putting it on the myself does anyone else remember these magic items? 

From what I can find on Google, I think you mean keen weapons, and I think they are from 3e. Killing Weapons are from Fire Emblem, and they have a critical rate of around 20% to 30% depending on the game. For 5e, the only weapon I recall that can crit on a 19 would be certain Moonblades.

Sounds like something you homebrewed up and forgot you homebrewed? Nothing comes up on DnDBeyond either through search or trying to add to a character sheet, nothing comes up when googled.  

Kinda the only answer left is you created it yourself

you would think but it's not in my collection

It is probably under someone else's collection. All homebrew is automatically shared between everyone in the campaign.