MsHeather,
Welcome and congratulations on your 402 days sober.
"Can a drug addict truly get and stay sober without rehab?"
That is an interesting question which I cannot answer. I would suggest posting your question in the "Substance Abuse" forum - there you will find more people with first hand experience with either trying to or sucessfully getting clean with and without the benefit of a rehab..
The "normal progression" for a heroin addict (my daughter) is detox, either cold turkey or rapid detox (less than a week) with some medication like Suboxone; then rehab, either residential or IOP; then perhaps a sober living house with fairly strict monitoring.
Insurance coverage and situations they will cover varies widely with company. Unfortunately, many insurance companies want you to try various IOP programs first and relapse before they will cover any type of a residential treatment facility.
The fact that, almost without exception, competent addiction counselors will tell you that the best chance for a lasting recovery starts with a residential rehab for at least a month is lost on the insurance companies -- they are basically interested in exhausting the cheaper options first usually at the expense of the patient's general health.
One day at a time,
Jim