I have been trying to collect every titan exotic armor piece and I already have every random drop exotic weapons but I still need some of the quest exotics but Xur can not give you those from the exotic engram and I also have every titan exotic except one so this week I was looking forward to buying it then having every titan exotic but went I bought it I got a titan exotic I already owned, the titan exotic was a shadowkeep exotic but I have owned shadowkeep for a while so I have no idea what happened I do not care about the legendary shards i lost but want to fix it so I get the exotic next week.
If the exotic your Titan is missing is Phoenix Cradle, then this is rewarded by completing the Shadowkeep campaign as a Titan and cannot be discovered from Exotic Engrams.