The drug would not have caused the psychosis imho. Normally a drug induced psychosis is just that - you take a drug you become psychotic and the episode eases as the drug leaves the system and residual problems are then mopped up.
Since the episode happened several days after the drug was took, (and didn't work), it sounds more like a proper psychotic episode possibly tied to a longer illness. Unfortunately when psychiatrists and the like here that a person with psychosis has been taking any drugs their first reaction is to label it drug induced and bounce the person to the addiction services, (yup even if it is only recreational use and like LSD not an addictive drug).
As for diagnosis - its a bit much to be labelling you Bi-polar after one episode and a two week illness. Unfortunately psychiatric diagnosis are at times very vague with the likes of schizophrenia used as an umbrella term and not an illness on it on per se.
The best advice I can give you is to eat well, avoid ALL drugs, (yes that includes alcohol and nicotine too), rest, exercise and occupy yourself with something healthy like playing an instrument. Keep a diary about how you are feeling and what you are experiencing but at the same time try not to get all caught up in looking for minutiae. Do a bit of reading on symptoms of psychiatric disorders instead of established 'illnessess', again don't go over board, just enough that you are aware of any potential problems. Do it with someone you trust implicitly if possible and write a letter to yourself asking yourself to trust that person even if you are thinking suspiciously of them.
I assume since they have diagnosed you they will have allocated a CPN? Engage with them but make sure they look up and are aware of drug induced psychosis and the fact that it occurs during or shortly after drug use, (normally more extended use too) with a resolution soon after. One night I believed that I was a giant and part of a giant world that overlapped and was destroying a minute world - every step killed millions, every pen stroke that I attempted to write myself a warning, (afraid I would forget when I came down), every shaky ill formed line crushed thousands. I was terrified at the destruction I was causing and was without a shadow of doubt psychotic. However a long sit some meditation and the passing the drug brought me back to reality - although the episode haunted me for days afterwards. Long story short I'm fine.
And yes you are right Drs do make mistakes and some times very serious mistakes. If you are functioning as you were prior to all this, (with the caveat that you were well!!!!), and no further episodes it is unlikely you have a psychiatric disorder, HOWEVER - if you do experience any other symptoms then it may be the case there is something that needs looking at more.
If as you say you don't believe it was the drugs and you don't believe you have a diagnosable psychiatric disorder, then how do you explain the psychotic episode? Were you at a time of severe pressure? Was there some big emotional disturbance occurring around then?
Hope this helps, take care.