Well if your drink was spiked you would have reported this to the police and in turn you'd have mentioned that you were in the process for applying for a career in the RN and subsequently alerted your AFCO to this fact?
(At least that's what I would have done)
To answer your question, no I don't think there is a CDT at PRNC. There certainly wasn't in 2011 when I did it.
Honesty is the best policy, Ninja has stated this many times.
If you push your look and get away undetected this time, ok, if they change at PRNC, they can if they wish, as the armed forces call it random testing for a reason, then if detected you have thrown your potential career away.
So your choice front up or take a risk with the rest of your life, the Navy's attitude to a failed drug test is you are out?
If you are concerned that a 'spiked drink' a few weeks ago may scupper your chances of joining up after all the hard work you have probably done to get to this point, then postpone your PRNC for a period of say, 2 years until the side affects of any 'spiked drinks' have time to wear off.