Can one hit of pot be detected?

It depends, if you're a daily user than yes it will, but if its one hit of weed and you havent smoked in months or years than it won't show up. I know from experience. If you take a huge hit and hold it in for a long time than it may stay in your system for 1-2 days, but other than that no.

As an analytical chemist, I agree with the previous answer. One hit done by a person who is not a regular user will probably not show up. Drug tests are not as sensitive as you would think, and one hit is going to be very hard to detect.