Not heard of any case histories like this with prostate but certainly not impossible as there have been rare cases where the immune system eventually recognises the cancer and you get a spontaneous remission. I'd certainly run checks again in terms of 3T mpMRI as these are really down to radiologist interpretation.
Did you have a TPM biopsy? Keep an eye on that PSA velocity. I foolishly left mine nearly 18 months after being given the all clear in Jan 2018 (PiRADS 2). Got a bit of a reality check when had PSA in July 2019 (5.6) and 3TmpMRI showed PiRADS 4 then biopsy confirmed give tumours in all four quadrants of prostate.