Well, I dont have 50 science... So I can't use that speech option, anything I can do to get him to realize the gun is missing? Thanks.

As far as I know, no.

The quest is unfinished, anyway.

Get at least 40 science and then get a magazine or get 30 science with the Followers Lab Coat and a magazine. If you don't have at least 30 science, then you have bigger problems.