Sustained release morphine has a half life of 12-24hours. You had a trigger,do you see that? Your mother in law. Learn from this. You relapsed in your head before you even took that pill. I hope you can look into some aftercare of NA, that will help a lot! Hang in there ((hugs))~Bkitty
I agree with LeaAnn try to get into some type of aftercare so you will develop the skills to deal with life's little surprises. So instead of making excuses your tools learned from aftercare will help you make decisions.
You would probably already be feeling WDs. You may have a light case compared to the methadone. You'll always be able to find an excuse if you look hard enough. I took them because it was Monday. Because it wasn't Monday. Because I was breathing. Because someone wouldn't treat me right. Because people treated me too well. LOL There was always something and always will be.
Try to look into some aftercare. Meetings. Counseling. Whatever works for you. Just find some support and some people to call when you get tempted! It really works, I promise!
I know nothing about morphine, so can't offer any insight into how long it will stay in your system. I'm sure someone will be along soon with some info.
My comment - your heart seems to be in the right place, but if you have access to meds, then your success may be in jeopardy. I believe that cutting all sources is the key to getting and staying clean. I've read so many times about someone relapsing because their dog is sick, or they had a bad day, or they are having trouble at work. Well, that is life; addicts can find hundreds of excuses a day to use, but if meds are there, then they won't.
If you really want to quit, then set up roadblocks - make it as close to impossible as you can to get meds. Then get aftercare - NA, AA, whatever. The answer is simple, but really, really hard to do.