If you want to PM me I can likely give you a list of MAT providers in your area john. As others have said, the ER will almost certainly not give you methadone, but it's likely they will give you something. Depending on the hospital/ER, they may not even give you something if they decide you're an addict or "drug seeker".
What dose of methadone were you on? I also will say to think very carefully about getting on methadone through the clinic. It's not such an issue as with others as you've been taking methadone for what seems like quite some time, but it's still a big change. From the little you've mentioned about your history, it kinda sounds like you may have problems using methadone as prescribed. That makes me think that the clinic may be a good option for you, but it's ultimately up to you. Consider your choices carefully.
Methadone stays in your system for a long time. Most clinics (at least those I'm aware of) will not deny care just because you had been taking methadone or that you have chronic pain issues. When the methadone shows up in your urine, say you had been getting it on the street or that you had to supplement your prescription with more methadone you got illegally. Don't just say it was from your script, it won't go as long a way in demonstrating to them that you're an acceptable MAT patient. I mean, a good clinic would accept you just on the grounds you cannot take your script as prescribed, but these are incredibly few and far between. The more you can demonstrate, or make them believe, not being on methadone at the clinic will put you at significant, real risk - from the police for engaging in illegal actions like buying methadone on the street; from overdosing; etc. etc. - the better the chances are they will accept you as a patient.
That you'd been taking methadone for pain dose complicate the issue, as most clinics explicitly will not treat chronic pain, only addiction. Most clinic won't treat chronic pain, but they also won't turn away a patient just because they suffer from chronic pain either. It's just that the methadone they will prescribe you isn't meant to be used to treat chronic pain or any issue other than addiction.
If you go in and tell them you're an addict and that the reason you had the script for methadone was because you were a drug seeker, that you can't control your use of your medication (the methadone you were prescribed), or something that will get them to see you as an addict first and foremost. It can be a double edged sword, in that you'll be labeled like that, but if you need the help ASAP it is probably your best bet.
Regarding the chronic pain issue, I would recommend (really this is something you should absolutely do) setting up an appointment with the clinic manager (either on the phone or in person) to talk about how they treat addiction, how the clinic works, your issues (that you can't take your meds as prescribed, are an addict, etc. etc.) and how your other conditions (e.g. chronic pain) will impact your MAT options. Ask lots of questions, write a list of questions you have before you call or see the manager so you're on your game, because this will really help you decide if the clinic is for you or even if it's a realistic option for you given your circumstances.
Can you find another doctor in your area to prescribed methadone for your condition? If you have the EKG and it shows the all clear and have other evidence of your condition warranting methadone, in a way (in terms of convenience that is) this would be far preferable to getting methadone from the clinic. That said, it kinda sounds like you have a problem taking your meds as prescribed, so the structure of taking methadone through the clinic sounds like the best option for you.
Best of luck OP. Sending you the big

Hope you get some relief ASAP.
BTW if you ever used DXM to get high, taking enough DXM for a first plateau dose will eliminate most of your withdrawal symptoms and make you feel infinitely better. Be careful about taking this, because there can be a lot of significant interactions between DXM and other medication (i.e. with an MAOI or SSRI/SNRI type antidepressant). It's amazing how well it work though, and I do highly recommend it. 150mg-300mg will totally blow your mind. In that you won't be in such crappy withdrawal anymore
