Hi,
I work in a data center and I have previous experience of such failure. I can try to assist you but before doing so, I would like to know :
1. Is it hardware RAID or software RAID? (you mentioned, you lost D drive so it should be windows, if not what is the OS and windows which version?)
2. You have configured RAID 1 or RAID 0?
3. Did you try to rebuild the RAID once again?
4. You can now, boot up the system but unable to find the D drive particularly, am I right?
5. Did you try to attach the secondary disk to another system and check that the data is present there or not? it is not getting detected by the other system?
if you wish, I can try.