I feel that it's a slippery slope to try to wonder if someone was malicious in intent(i.e., awful person that hid it well) because it leads to a sense of victimization, which adds more to cope with.
It's a sad feeling to not get closure. Have you made any further attempts at gentle asking to have a mature discussion about what happened? You may not like the answers, yet closure really is helpful in the healing process.

What leads you to wonder about bipolar depression? Are there known symptoms in his past?