Man, that's crazy. I didn't think an over-the-counter drug could cause full blown HPPD. Sounds like it's a nervous-system stimulant that acts on dopamine and serotonin, which certainly isn't something I imagine is great for our condition. I just can't believe it had such a severely negative effect.
You should definitely talk to your doctor and let them know this happened, maybe even get in contact with the manufacturers if possible. There are a lot of stories from people who've relapsed so maybe you can read their posts and see what they said. I imagine if you healed once you can heal again.