I was planning on writing exactly what FluffyDinosaur wrote above.

Obviously we don't know all the details of your hospital visit, but I can say that sometimes (not always) psychiatrists at psych hospitals don't have the big picture to go on. Some only spend very limited time with the hospital patients, and only see one presentation/episode during a patient's stay. Also, sometimes what is said in the hospital consultations can be misleading if taken all alone. I mean, if I went to the hospital in a depressive episode and talked about a trauma, does that mean I don't have bipolar disorder then? Would that mean I only have PTSD, major depressive disorder, and/or something else other than bipolar disorder? Despite having had multiple manic episodes in the past?

I would certainly hope that the hospital psychiatrist had a long talk with your regular psychiatrist before issuing a diagnosis and overhauling your medications. However, I am quite sure that many simply don't. Have you asked your outpatient (regular) psychiatrist if he/she was consulted by the hospital psychiatrist?

Many hospital and IOP/PHP psychiatrists in the past have done me more harm than good because they never consulted with my outpatient psychiatrist.

Luckily, I have been with my outpatient (regular) psychiatrist for many years now. He has seen/observed, and heard everything from me. The disadvantage of only having a psychiatrist or therapist for a limited time, or during a period when the illness presents in a single way, is that it causes uncertainty about dx.