Sattivas produce heady highs. What that means is that your high will be more of a "trippy" like high as opposed to Indica where your high will be more of a body type high. The reason it happens to you is probably not because of bipolar disorder. You're just stoned. If that happened while you were sober, then maybe it could be Bipolar.

After rereading your post again, you are absolutely positive that no thoughts are causing this dramatic mood shift? Usually it is our own thoughts that cause us to panic. Maybe try to get stoned off sattiva again and analyze what you are experiencing. Write it down. That would give us, and especially yourself, greater insight into what's happening to you during those moments.

Random, but maybe it applies:

Perhaps being high is likened to pain. When we experience pain our bodies experience it the same. I.E. if I were to get stabbed and you were too then we would have the same pain level. Although, suppose your tougher then me and can withstand the pain better then I'm able to. It doesn't mean that we both don't experience the same amount of pain, it's just that you are better able to deal with it. I think the same can be applied to getting stoned or any sort of experience for that matter.

Dunno just throwing that out there.