I don't think even you believe that. As far as we know Earth is the richest and most diverse life-based resource in the galaxy. Any scientist worth their salt (or whatever equivalent compounds) would realise they'd hit the mother lode.
If you can travel through space and time, you could probably determine every possible chemical combination. Honestly that's the future of pharmacology, hit a receptor or binding site with random chemicals until something "fits".
Plus you are assuming that scientist are running the show. What if it's drunken frat boys.