HP Proliant DL380 RAID 5 Server not booting completely

Yes, I’m stupid, so please take it into consideration. I manage a server that has a RAID 5 on it. Not knowing what I was doing, I removed the hard drive in Slot 0 and then put the same drive back in to the same slot. Now the server won’t boot completely.

After booting, I see this message “Slot 0 HP Smart Array 5i Controller Initializing” for a good amount of time. Then is says 1784 Slot 0 Drive Drive Array Failure. Then it tries to boot Cd, floppy, hard, and NIC. It ends up with Non system disk or disk error. Replace and strike any key when ready.

It’s a HP Proliant DL380.

So, how screwed am I and what can I do to repair the damage?