As mentioned, sometimes pdocs are moving into a different practice and cannot take clients with them because clients are the "property" of the practice. When this is the case, and if they can be located, the client may then contact the pdoc and ask if s/he is accepting new clients in his/her new practice.
I'm surprised your pdoc did not help to connect you with a pdoc prior to leaving. The pdoc you've been seeing has pertinent info to share with any new pdoc.
I hope your transition for care goes smoothly.

WC