I wasn't searched on entry either, but turning a blind eye to hash seems to be a bit far in the opposite direction of lenient for a detox clinic to me. Especially as there are increasing numbers of people in detox for cannabis. Nipping over to the pub for a pint seems pretty lax too!
I think the boozers had the tendancy to show the most denial over their behaviour from my experience, but I have no idea whether that's a fair generalisation to make. One of the counsellors did say that in his experience boozers tended to underestimate their habit and drug users would overestimate.