I can tell you, my AH did the very same thing. He agreed to detox and then intensive outpatient. He went for a bit and then quit, saying he'll just get therapy. He never did, he was using the whole time, even in outpatient. He continued to use and I had finally had enough and started packing his bags for him and then he grabbed a bottle of pills and threatened suicide. So I calmly told him I will call the police and 302 him then if he is going to harm himself or he could simply go back into treatment. He begged for just detox and intensive outpatient again because "he already knows what to do". I didn't cave in and now he's out of state at a 30 day inpatient. I'm trying not to be too hopeful but he seems like he's coming around.
Trust your instincts. If it doesn't seem right, it isn't. Drug tests are very easy to fool, especially if they are planned. They all think they can do it on their own and that what rehabs preach are pointless and stupid. Fact is, they can't do it on their own. Just therapy doesn't work. He is trying to manipulate you by threatening to hurt himself. Don't cave in. Hold your ground. Sending prayers and thoughts