On a side note, where is this located? That cop looks like as if he is from the U.K.
Pretty sure it's New Zealand.
And no, the police didn't fuck up... they entered the property legally and, in so doing, observed something that either led to suspicion of an offence (which gives grounds for arrest / search) and/or items were in plain sight... The would have fucked up if they'd simply ignored the drugs paraphernalia as 'unrelated' to the person they were looking for.